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1 | Open vSwitch <http://openvswitch.org> |
2 | ||
3 | Frequently Asked Questions | |
4 | ========================== | |
5 | ||
3fc7dc18 JP |
6 | General |
7 | ------- | |
8 | ||
9 | Q: What is Open vSwitch? | |
10 | ||
11 | A: Open vSwitch is a production quality open source software switch | |
29089a54 RL |
12 | designed to be used as a vswitch in virtualized server |
13 | environments. A vswitch forwards traffic between different VMs on | |
14 | the same physical host and also forwards traffic between VMs and | |
15 | the physical network. Open vSwitch supports standard management | |
16 | interfaces (e.g. sFlow, NetFlow, IPFIX, RSPAN, CLI), and is open to | |
17 | programmatic extension and control using OpenFlow and the OVSDB | |
18 | management protocol. | |
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19 | |
20 | Open vSwitch as designed to be compatible with modern switching | |
21 | chipsets. This means that it can be ported to existing high-fanout | |
22 | switches allowing the same flexible control of the physical | |
23 | infrastructure as the virtual infrastructure. It also means that | |
24 | Open vSwitch will be able to take advantage of on-NIC switching | |
25 | chipsets as their functionality matures. | |
26 | ||
27 | Q: What virtualization platforms can use Open vSwitch? | |
28 | ||
29 | A: Open vSwitch can currently run on any Linux-based virtualization | |
37418c86 | 30 | platform (kernel 2.6.32 and newer), including: KVM, VirtualBox, Xen, |
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31 | Xen Cloud Platform, XenServer. As of Linux 3.3 it is part of the |
32 | mainline kernel. The bulk of the code is written in platform- | |
33 | independent C and is easily ported to other environments. We welcome | |
34 | inquires about integrating Open vSwitch with other virtualization | |
35 | platforms. | |
36 | ||
37 | Q: How can I try Open vSwitch? | |
38 | ||
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39 | A: The Open vSwitch source code can be built on a Linux system. You can |
40 | build and experiment with Open vSwitch on any Linux machine. | |
41 | Packages for various Linux distributions are available on many | |
42 | platforms, including: Debian, Ubuntu, Fedora. | |
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43 | |
44 | You may also download and run a virtualization platform that already | |
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45 | has Open vSwitch integrated. For example, download a recent ISO for |
46 | XenServer or Xen Cloud Platform. Be aware that the version | |
47 | integrated with a particular platform may not be the most recent Open | |
48 | vSwitch release. | |
49 | ||
50 | Q: Does Open vSwitch only work on Linux? | |
51 | ||
52 | A: No, Open vSwitch has been ported to a number of different operating | |
53 | systems and hardware platforms. Most of the development work occurs | |
54 | on Linux, but the code should be portable to any POSIX system. We've | |
55 | seen Open vSwitch ported to a number of different platforms, | |
56 | including FreeBSD, Windows, and even non-POSIX embedded systems. | |
57 | ||
58 | By definition, the Open vSwitch Linux kernel module only works on | |
59 | Linux and will provide the highest performance. However, a userspace | |
60 | datapath is available that should be very portable. | |
61 | ||
62 | Q: What's involved with porting Open vSwitch to a new platform or | |
63 | switching ASIC? | |
64 | ||
65 | A: The PORTING document describes how one would go about porting Open | |
66 | vSwitch to a new operating system or hardware platform. | |
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67 | |
68 | Q: Why would I use Open vSwitch instead of the Linux bridge? | |
69 | ||
70 | A: Open vSwitch is specially designed to make it easier to manage VM | |
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71 | network configuration and monitor state spread across many physical |
72 | hosts in dynamic virtualized environments. Please see WHY-OVS for a | |
73 | more detailed description of how Open vSwitch relates to the Linux | |
74 | Bridge. | |
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75 | |
76 | Q: How is Open vSwitch related to distributed virtual switches like the | |
77 | VMware vNetwork distributed switch or the Cisco Nexus 1000V? | |
78 | ||
79 | A: Distributed vswitch applications (e.g., VMware vNetwork distributed | |
80 | switch, Cisco Nexus 1000V) provide a centralized way to configure and | |
81 | monitor the network state of VMs that are spread across many physical | |
82 | hosts. Open vSwitch is not a distributed vswitch itself, rather it | |
83 | runs on each physical host and supports remote management in a way | |
84 | that makes it easier for developers of virtualization/cloud | |
85 | management platforms to offer distributed vswitch capabilities. | |
86 | ||
87 | To aid in distribution, Open vSwitch provides two open protocols that | |
88 | are specially designed for remote management in virtualized network | |
89 | environments: OpenFlow, which exposes flow-based forwarding state, | |
90 | and the OVSDB management protocol, which exposes switch port state. | |
91 | In addition to the switch implementation itself, Open vSwitch | |
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92 | includes tools (ovs-ofctl, ovs-vsctl) that developers can script and |
93 | extend to provide distributed vswitch capabilities that are closely | |
94 | integrated with their virtualization management platform. | |
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95 | |
96 | Q: Why doesn't Open vSwitch support distribution? | |
97 | ||
98 | A: Open vSwitch is intended to be a useful component for building | |
99 | flexible network infrastructure. There are many different approaches | |
100 | to distribution which balance trade-offs between simplicity, | |
101 | scalability, hardware compatibility, convergence times, logical | |
102 | forwarding model, etc. The goal of Open vSwitch is to be able to | |
103 | support all as a primitive building block rather than choose a | |
104 | particular point in the distributed design space. | |
105 | ||
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106 | Q: How can I contribute to the Open vSwitch Community? |
107 | ||
108 | A: You can start by joining the mailing lists and helping to answer | |
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109 | questions. You can also suggest improvements to documentation. If |
110 | you have a feature or bug you would like to work on, send a mail to | |
111 | one of the mailing lists: | |
112 | ||
113 | http://openvswitch.org/mlists/ | |
114 | ||
115 | ||
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116 | Releases |
117 | -------- | |
118 | ||
119 | Q: What does it mean for an Open vSwitch release to be LTS (long-term | |
120 | support)? | |
3fc7dc18 | 121 | |
7b287e99 JP |
122 | A: All official releases have been through a comprehensive testing |
123 | process and are suitable for production use. Planned releases will | |
124 | occur several times a year. If a significant bug is identified in an | |
125 | LTS release, we will provide an updated release that includes the | |
126 | fix. Releases that are not LTS may not be fixed and may just be | |
127 | supplanted by the next major release. The current LTS release is | |
79a6e10e | 128 | 1.9.x. |
7b287e99 | 129 | |
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130 | Q: What Linux kernel versions does each Open vSwitch release work with? |
131 | ||
132 | A: The following table lists the Linux kernel versions against which the | |
133 | given versions of the Open vSwitch kernel module will successfully | |
134 | build. The Linux kernel versions are upstream kernel versions, so | |
a01b5c51 BP |
135 | Linux kernels modified from the upstream sources may not build in |
136 | some cases even if they are based on a supported version. This is | |
137 | most notably true of Red Hat Enterprise Linux (RHEL) kernels, which | |
138 | are extensively modified from upstream. | |
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139 | |
140 | Open vSwitch Linux kernel | |
141 | ------------ ------------- | |
142 | 1.4.x 2.6.18 to 3.2 | |
143 | 1.5.x 2.6.18 to 3.2 | |
144 | 1.6.x 2.6.18 to 3.2 | |
145 | 1.7.x 2.6.18 to 3.3 | |
146 | 1.8.x 2.6.18 to 3.4 | |
64807dfb | 147 | 1.9.x 2.6.18 to 3.8 |
889be6f9 JG |
148 | 1.10.x 2.6.18 to 3.8 |
149 | 1.11.x 2.6.18 to 3.8 | |
31d73806 | 150 | 2.0.x 2.6.32 to 3.10 |
25a7a1ca | 151 | 2.1.x 2.6.32 to 3.11 |
e2f3178f | 152 | 2.2.x 2.6.32 to 3.14 |
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153 | |
154 | Open vSwitch userspace should also work with the Linux kernel module | |
155 | built into Linux 3.3 and later. | |
156 | ||
157 | Open vSwitch userspace is not sensitive to the Linux kernel version. | |
37418c86 | 158 | It should build against almost any kernel, certainly against 2.6.32 |
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159 | and later. |
160 | ||
a7ae9380 | 161 | Q: I get an error like this when I configure Open vSwitch: |
29089a54 | 162 | |
a7ae9380 BP |
163 | configure: error: Linux kernel in <dir> is version <x>, but |
164 | version newer than <y> is not supported (please refer to the | |
165 | FAQ for advice) | |
29089a54 | 166 | |
a7ae9380 | 167 | What should I do? |
33cec590 | 168 | |
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169 | A: If there is a newer version of Open vSwitch, consider building that |
170 | one, because it may support the kernel that you are building | |
171 | against. (To find out, consult the table in the previous answer.) | |
172 | ||
173 | Otherwise, use the Linux kernel module supplied with the kernel | |
174 | that you are using. All versions of Open vSwitch userspace are | |
175 | compatible with all versions of the Open vSwitch kernel module, so | |
176 | this will also work. See also the following question. | |
33cec590 | 177 | |
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178 | Q: What features are not available in the Open vSwitch kernel datapath |
179 | that ships as part of the upstream Linux kernel? | |
180 | ||
9c333bff JG |
181 | A: The kernel module in upstream Linux does not include support for |
182 | LISP. Work is in progress to add support for LISP to the upstream | |
183 | Linux version of the Open vSwitch kernel module. For now, if you | |
184 | need this feature, use the kernel module from the Open vSwitch | |
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185 | distribution instead of the upstream Linux kernel module. |
186 | ||
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187 | Certain features require kernel support to function or to have |
188 | reasonable performance. If the ovs-vswitchd log file indicates that | |
189 | a feature is not supported, consider upgrading to a newer upstream | |
190 | Linux release or using the kernel module paired with the userspace | |
191 | distribution. | |
6302c641 | 192 | |
6814c630 JG |
193 | Q: Why do tunnels not work when using a kernel module other than the |
194 | one packaged with Open vSwitch? | |
195 | ||
196 | A: Support for tunnels was added to the upstream Linux kernel module | |
197 | after the rest of Open vSwitch. As a result, some kernels may contain | |
198 | support for Open vSwitch but not tunnels. The minimum kernel version | |
199 | that supports each tunnel protocol is: | |
200 | ||
201 | Protocol Linux Kernel | |
202 | -------- ------------ | |
203 | GRE 3.11 | |
204 | VXLAN 3.12 | |
205 | LISP <not upstream> | |
206 | ||
207 | If you are using a version of the kernel that is older than the one | |
208 | listed above, it is still possible to use that tunnel protocol. However, | |
209 | you must compile and install the kernel module included with the Open | |
210 | vSwitch distribution rather than the one on your machine. If problems | |
211 | persist after doing this, check to make sure that the module that is | |
212 | loaded is the one you expect. | |
213 | ||
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214 | Q: What features are not available when using the userspace datapath? |
215 | ||
0a740f48 | 216 | A: Tunnel virtual ports are not supported, as described in the |
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217 | previous answer. It is also not possible to use queue-related |
218 | actions. On Linux kernels before 2.6.39, maximum-sized VLAN packets | |
219 | may not be transmitted. | |
3fc7dc18 | 220 | |
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221 | Q: What Linux kernel versions does IPFIX flow monitoring work with? |
222 | ||
223 | A: IPFIX flow monitoring requires the Linux kernel module from Open | |
224 | vSwitch version 1.10.90 or later. | |
225 | ||
226 | Q: Should userspace or kernel be upgraded first to minimize downtime? | |
227 | ||
228 | In general, the Open vSwitch userspace should be used with the | |
229 | kernel version included in the same release or with the version | |
230 | from upstream Linux. However, when upgrading between two releases | |
231 | of Open vSwitch it is best to migrate userspace first to reduce | |
232 | the possibility of incompatibilities. | |
233 | ||
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234 | Q: What happened to the bridge compatibility feature? |
235 | ||
236 | A: Bridge compatibility was a feature of Open vSwitch 1.9 and earlier. | |
237 | When it was enabled, Open vSwitch imitated the interface of the | |
238 | Linux kernel "bridge" module. This allowed users to drop Open | |
239 | vSwitch into environments designed to use the Linux kernel bridge | |
240 | module without adapting the environment to use Open vSwitch. | |
241 | ||
242 | Open vSwitch 1.10 and later do not support bridge compatibility. | |
243 | The feature was dropped because version 1.10 adopted a new internal | |
244 | architecture that made bridge compatibility difficult to maintain. | |
245 | Now that many environments use OVS directly, it would be rarely | |
246 | useful in any case. | |
247 | ||
248 | To use bridge compatibility, install OVS 1.9 or earlier, including | |
249 | the accompanying kernel modules (both the main and bridge | |
250 | compatibility modules), following the instructions that come with | |
251 | the release. Be sure to start the ovs-brcompatd daemon. | |
252 | ||
3fc7dc18 | 253 | |
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254 | Terminology |
255 | ----------- | |
256 | ||
257 | Q: I thought Open vSwitch was a virtual Ethernet switch, but the | |
258 | documentation keeps talking about bridges. What's a bridge? | |
259 | ||
260 | A: In networking, the terms "bridge" and "switch" are synonyms. Open | |
261 | vSwitch implements an Ethernet switch, which means that it is also | |
262 | an Ethernet bridge. | |
263 | ||
264 | Q: What's a VLAN? | |
265 | ||
266 | A: See the "VLAN" section below. | |
267 | ||
268 | ||
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269 | Basic Configuration |
270 | ------------------- | |
271 | ||
272 | Q: How do I configure a port as an access port? | |
273 | ||
274 | A: Add "tag=VLAN" to your "ovs-vsctl add-port" command. For example, | |
275 | the following commands configure br0 with eth0 as a trunk port (the | |
276 | default) and tap0 as an access port for VLAN 9: | |
277 | ||
278 | ovs-vsctl add-br br0 | |
279 | ovs-vsctl add-port br0 eth0 | |
280 | ovs-vsctl add-port br0 tap0 tag=9 | |
281 | ||
282 | If you want to configure an already added port as an access port, | |
283 | use "ovs-vsctl set", e.g.: | |
284 | ||
285 | ovs-vsctl set port tap0 tag=9 | |
286 | ||
287 | Q: How do I configure a port as a SPAN port, that is, enable mirroring | |
288 | of all traffic to that port? | |
289 | ||
290 | A: The following commands configure br0 with eth0 and tap0 as trunk | |
291 | ports. All traffic coming in or going out on eth0 or tap0 is also | |
292 | mirrored to tap1; any traffic arriving on tap1 is dropped: | |
293 | ||
294 | ovs-vsctl add-br br0 | |
295 | ovs-vsctl add-port br0 eth0 | |
296 | ovs-vsctl add-port br0 tap0 | |
297 | ovs-vsctl add-port br0 tap1 \ | |
298 | -- --id=@p get port tap1 \ | |
0dc8b8c2 YT |
299 | -- --id=@m create mirror name=m0 select-all=true output-port=@p \ |
300 | -- set bridge br0 mirrors=@m | |
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301 | |
302 | To later disable mirroring, run: | |
303 | ||
304 | ovs-vsctl clear bridge br0 mirrors | |
305 | ||
e253f732 BP |
306 | Q: Does Open vSwitch support configuring a port in promiscuous mode? |
307 | ||
308 | A: Yes. How you configure it depends on what you mean by "promiscuous | |
309 | mode": | |
310 | ||
311 | - Conventionally, "promiscuous mode" is a feature of a network | |
312 | interface card. Ordinarily, a NIC passes to the CPU only the | |
313 | packets actually destined to its host machine. It discards | |
314 | the rest to avoid wasting memory and CPU cycles. When | |
315 | promiscuous mode is enabled, however, it passes every packet | |
316 | to the CPU. On an old-style shared-media or hub-based | |
317 | network, this allows the host to spy on all packets on the | |
318 | network. But in the switched networks that are almost | |
319 | everywhere these days, promiscuous mode doesn't have much | |
320 | effect, because few packets not destined to a host are | |
321 | delivered to the host's NIC. | |
322 | ||
323 | This form of promiscuous mode is configured in the guest OS of | |
324 | the VMs on your bridge, e.g. with "ifconfig". | |
325 | ||
326 | - The VMware vSwitch uses a different definition of "promiscuous | |
327 | mode". When you configure promiscuous mode on a VMware vNIC, | |
328 | the vSwitch sends a copy of every packet received by the | |
329 | vSwitch to that vNIC. That has a much bigger effect than just | |
330 | enabling promiscuous mode in a guest OS. Rather than getting | |
331 | a few stray packets for which the switch does not yet know the | |
332 | correct destination, the vNIC gets every packet. The effect | |
333 | is similar to replacing the vSwitch by a virtual hub. | |
334 | ||
335 | This "promiscuous mode" is what switches normally call "port | |
336 | mirroring" or "SPAN". For information on how to configure | |
337 | SPAN, see "How do I configure a port as a SPAN port, that is, | |
338 | enable mirroring of all traffic to that port?" | |
339 | ||
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340 | Q: How do I configure a VLAN as an RSPAN VLAN, that is, enable |
341 | mirroring of all traffic to that VLAN? | |
342 | ||
343 | A: The following commands configure br0 with eth0 as a trunk port and | |
344 | tap0 as an access port for VLAN 10. All traffic coming in or going | |
345 | out on tap0, as well as traffic coming in or going out on eth0 in | |
346 | VLAN 10, is also mirrored to VLAN 15 on eth0. The original tag for | |
347 | VLAN 10, in cases where one is present, is dropped as part of | |
348 | mirroring: | |
349 | ||
350 | ovs-vsctl add-br br0 | |
351 | ovs-vsctl add-port br0 eth0 | |
352 | ovs-vsctl add-port br0 tap0 tag=10 | |
353 | ovs-vsctl \ | |
0dc8b8c2 | 354 | -- --id=@m create mirror name=m0 select-all=true select-vlan=10 \ |
717e7c8d | 355 | output-vlan=15 \ |
0dc8b8c2 | 356 | -- set bridge br0 mirrors=@m |
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357 | |
358 | To later disable mirroring, run: | |
359 | ||
360 | ovs-vsctl clear bridge br0 mirrors | |
361 | ||
362 | Mirroring to a VLAN can disrupt a network that contains unmanaged | |
363 | switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a | |
364 | GRE tunnel has fewer caveats than mirroring to a VLAN and should | |
365 | generally be preferred. | |
366 | ||
367 | Q: Can I mirror more than one input VLAN to an RSPAN VLAN? | |
368 | ||
369 | A: Yes, but mirroring to a VLAN strips the original VLAN tag in favor | |
370 | of the specified output-vlan. This loss of information may make | |
371 | the mirrored traffic too hard to interpret. | |
372 | ||
373 | To mirror multiple VLANs, use the commands above, but specify a | |
374 | comma-separated list of VLANs as the value for select-vlan. To | |
375 | mirror every VLAN, use the commands above, but omit select-vlan and | |
376 | its value entirely. | |
377 | ||
378 | When a packet arrives on a VLAN that is used as a mirror output | |
379 | VLAN, the mirror is disregarded. Instead, in standalone mode, OVS | |
380 | floods the packet across all the ports for which the mirror output | |
381 | VLAN is configured. (If an OpenFlow controller is in use, then it | |
382 | can override this behavior through the flow table.) If OVS is used | |
383 | as an intermediate switch, rather than an edge switch, this ensures | |
384 | that the RSPAN traffic is distributed through the network. | |
385 | ||
386 | Mirroring to a VLAN can disrupt a network that contains unmanaged | |
387 | switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a | |
388 | GRE tunnel has fewer caveats than mirroring to a VLAN and should | |
389 | generally be preferred. | |
390 | ||
391 | Q: How do I configure mirroring of all traffic to a GRE tunnel? | |
392 | ||
393 | A: The following commands configure br0 with eth0 and tap0 as trunk | |
394 | ports. All traffic coming in or going out on eth0 or tap0 is also | |
395 | mirrored to gre0, a GRE tunnel to the remote host 192.168.1.10; any | |
396 | traffic arriving on gre0 is dropped: | |
397 | ||
398 | ovs-vsctl add-br br0 | |
399 | ovs-vsctl add-port br0 eth0 | |
400 | ovs-vsctl add-port br0 tap0 | |
401 | ovs-vsctl add-port br0 gre0 \ | |
402 | -- set interface gre0 type=gre options:remote_ip=192.168.1.10 \ | |
403 | -- --id=@p get port gre0 \ | |
0dc8b8c2 YT |
404 | -- --id=@m create mirror name=m0 select-all=true output-port=@p \ |
405 | -- set bridge br0 mirrors=@m | |
717e7c8d BP |
406 | |
407 | To later disable mirroring and destroy the GRE tunnel: | |
408 | ||
409 | ovs-vsctl clear bridge br0 mirrors | |
410 | ovs-vcstl del-port br0 gre0 | |
411 | ||
412 | Q: Does Open vSwitch support ERSPAN? | |
413 | ||
414 | A: No. ERSPAN is an undocumented proprietary protocol. As an | |
415 | alternative, Open vSwitch supports mirroring to a GRE tunnel (see | |
416 | above). | |
417 | ||
1ab9712b BP |
418 | Q: How do I connect two bridges? |
419 | ||
420 | A: First, why do you want to do this? Two connected bridges are not | |
421 | much different from a single bridge, so you might as well just have | |
422 | a single bridge with all your ports on it. | |
423 | ||
424 | If you still want to connect two bridges, you can use a pair of | |
425 | patch ports. The following example creates bridges br0 and br1, | |
426 | adds eth0 and tap0 to br0, adds tap1 to br1, and then connects br0 | |
427 | and br1 with a pair of patch ports. | |
428 | ||
429 | ovs-vsctl add-br br0 | |
430 | ovs-vsctl add-port br0 eth0 | |
431 | ovs-vsctl add-port br0 tap0 | |
432 | ovs-vsctl add-br br1 | |
433 | ovs-vsctl add-port br1 tap1 | |
434 | ovs-vsctl \ | |
435 | -- add-port br0 patch0 \ | |
436 | -- set interface patch0 type=patch options:peer=patch1 \ | |
437 | -- add-port br1 patch1 \ | |
438 | -- set interface patch1 type=patch options:peer=patch0 | |
439 | ||
440 | Bridges connected with patch ports are much like a single bridge. | |
441 | For instance, if the example above also added eth1 to br1, and both | |
442 | eth0 and eth1 happened to be connected to the same next-hop switch, | |
443 | then you could loop your network just as you would if you added | |
444 | eth0 and eth1 to the same bridge (see the "Configuration Problems" | |
445 | section below for more information). | |
446 | ||
447 | If you are using Open vSwitch 1.9 or an earlier version, then you | |
448 | need to be using the kernel module bundled with Open vSwitch rather | |
449 | than the one that is integrated into Linux 3.3 and later, because | |
450 | Open vSwitch 1.9 and earlier versions need kernel support for patch | |
451 | ports. This also means that in Open vSwitch 1.9 and earlier, patch | |
452 | ports will not work with the userspace datapath, only with the | |
453 | kernel module. | |
454 | ||
5c9c1105 YT |
455 | Q: How do I configure a bridge without an OpenFlow local port? |
456 | (Local port in the sense of OFPP_LOCAL) | |
457 | ||
458 | A: Open vSwitch does not support such a configuration. | |
459 | Bridges always have their local ports. | |
460 | ||
1a274bfe BP |
461 | |
462 | Implementation Details | |
463 | ---------------------- | |
464 | ||
465 | Q: I hear OVS has a couple of kinds of flows. Can you tell me about them? | |
a70fc0cf JP |
466 | |
467 | A: Open vSwitch uses different kinds of flows for different purposes: | |
468 | ||
469 | - OpenFlow flows are the most important kind of flow. OpenFlow | |
470 | controllers use these flows to define a switch's policy. | |
471 | OpenFlow flows support wildcards, priorities, and multiple | |
472 | tables. | |
473 | ||
474 | When in-band control is in use, Open vSwitch sets up a few | |
475 | "hidden" flows, with priority higher than a controller or the | |
476 | user can configure, that are not visible via OpenFlow. (See | |
477 | the "Controller" section of the FAQ for more information | |
478 | about hidden flows.) | |
479 | ||
480 | - The Open vSwitch software switch implementation uses a second | |
d9cb84ff BP |
481 | kind of flow internally. These flows, called "datapath" or |
482 | "kernel" flows, do not support priorities and comprise only a | |
483 | single table, which makes them suitable for caching. (Like | |
484 | OpenFlow flows, datapath flows do support wildcarding, in Open | |
485 | vSwitch 1.11 and later.) OpenFlow flows and datapath flows | |
a70fc0cf JP |
486 | also support different actions and number ports differently. |
487 | ||
d9cb84ff BP |
488 | Datapath flows are an implementation detail that is subject to |
489 | change in future versions of Open vSwitch. Even with the | |
490 | current version of Open vSwitch, hardware switch | |
491 | implementations do not necessarily use this architecture. | |
a70fc0cf | 492 | |
1a274bfe BP |
493 | Users and controllers directly control only the OpenFlow flow |
494 | table. Open vSwitch manages the datapath flow table itself, so | |
495 | users should not normally be concerned with it. | |
496 | ||
497 | Q: Why are there so many different ways to dump flows? | |
498 | ||
499 | A: Open vSwitch has two kinds of flows (see the previous question), so | |
500 | it has commands with different purposes for dumping each kind of | |
501 | flow: | |
a70fc0cf JP |
502 | |
503 | - "ovs-ofctl dump-flows <br>" dumps OpenFlow flows, excluding | |
504 | hidden flows. This is the most commonly useful form of flow | |
505 | dump. (Unlike the other commands, this should work with any | |
506 | OpenFlow switch, not just Open vSwitch.) | |
507 | ||
508 | - "ovs-appctl bridge/dump-flows <br>" dumps OpenFlow flows, | |
509 | including hidden flows. This is occasionally useful for | |
510 | troubleshooting suspected issues with in-band control. | |
511 | ||
d9cb84ff | 512 | - "ovs-dpctl dump-flows [dp]" dumps the datapath flow table |
a70fc0cf | 513 | entries for a Linux kernel-based datapath. In Open vSwitch |
acaaa4b4 BP |
514 | 1.10 and later, ovs-vswitchd merges multiple switches into a |
515 | single datapath, so it will show all the flows on all your | |
516 | kernel-based switches. This command can occasionally be | |
a70fc0cf JP |
517 | useful for debugging. |
518 | ||
519 | - "ovs-appctl dpif/dump-flows <br>", new in Open vSwitch 1.10, | |
d9cb84ff BP |
520 | dumps datapath flows for only the specified bridge, regardless |
521 | of the type. | |
a70fc0cf | 522 | |
c81f359b FL |
523 | Q: How does multicast snooping works with VLANs? |
524 | ||
525 | A: Open vSwitch maintains snooping tables for each VLAN. | |
526 | ||
717e7c8d | 527 | |
bcb8bde4 JR |
528 | Performance |
529 | ----------- | |
530 | ||
531 | Q: I just upgraded and I see a performance drop. Why? | |
532 | ||
533 | A: The OVS kernel datapath may have been updated to a newer version than | |
534 | the OVS userspace components. Sometimes new versions of OVS kernel | |
535 | module add functionality that is backwards compatible with older | |
536 | userspace components but may cause a drop in performance with them. | |
537 | Especially, if a kernel module from OVS 2.1 or newer is paired with | |
538 | OVS userspace 1.10 or older, there will be a performance drop for | |
539 | TCP traffic. | |
540 | ||
541 | Updating the OVS userspace components to the latest released | |
542 | version should fix the performance degradation. | |
543 | ||
544 | To get the best possible performance and functionality, it is | |
545 | recommended to pair the same versions of the kernel module and OVS | |
546 | userspace. | |
547 | ||
548 | ||
c483d489 BP |
549 | Configuration Problems |
550 | ---------------------- | |
551 | ||
552 | Q: I created a bridge and added my Ethernet port to it, using commands | |
553 | like these: | |
554 | ||
555 | ovs-vsctl add-br br0 | |
556 | ovs-vsctl add-port br0 eth0 | |
557 | ||
558 | and as soon as I ran the "add-port" command I lost all connectivity | |
559 | through eth0. Help! | |
560 | ||
561 | A: A physical Ethernet device that is part of an Open vSwitch bridge | |
562 | should not have an IP address. If one does, then that IP address | |
563 | will not be fully functional. | |
564 | ||
565 | You can restore functionality by moving the IP address to an Open | |
566 | vSwitch "internal" device, such as the network device named after | |
567 | the bridge itself. For example, assuming that eth0's IP address is | |
568 | 192.168.128.5, you could run the commands below to fix up the | |
569 | situation: | |
570 | ||
571 | ifconfig eth0 0.0.0.0 | |
572 | ifconfig br0 192.168.128.5 | |
573 | ||
574 | (If your only connection to the machine running OVS is through the | |
575 | IP address in question, then you would want to run all of these | |
576 | commands on a single command line, or put them into a script.) If | |
577 | there were any additional routes assigned to eth0, then you would | |
578 | also want to use commands to adjust these routes to go through br0. | |
579 | ||
580 | If you use DHCP to obtain an IP address, then you should kill the | |
581 | DHCP client that was listening on the physical Ethernet interface | |
582 | (e.g. eth0) and start one listening on the internal interface | |
583 | (e.g. br0). You might still need to manually clear the IP address | |
584 | from the physical interface (e.g. with "ifconfig eth0 0.0.0.0"). | |
585 | ||
586 | There is no compelling reason why Open vSwitch must work this way. | |
587 | However, this is the way that the Linux kernel bridge module has | |
588 | always worked, so it's a model that those accustomed to Linux | |
589 | bridging are already used to. Also, the model that most people | |
590 | expect is not implementable without kernel changes on all the | |
591 | versions of Linux that Open vSwitch supports. | |
592 | ||
593 | By the way, this issue is not specific to physical Ethernet | |
594 | devices. It applies to all network devices except Open vswitch | |
595 | "internal" devices. | |
596 | ||
597 | Q: I created a bridge and added a couple of Ethernet ports to it, | |
598 | using commands like these: | |
599 | ||
600 | ovs-vsctl add-br br0 | |
601 | ovs-vsctl add-port br0 eth0 | |
602 | ovs-vsctl add-port br0 eth1 | |
603 | ||
604 | and now my network seems to have melted: connectivity is unreliable | |
605 | (even connectivity that doesn't go through Open vSwitch), all the | |
629a6b48 BP |
606 | LEDs on my physical switches are blinking, wireshark shows |
607 | duplicated packets, and CPU usage is very high. | |
c483d489 BP |
608 | |
609 | A: More than likely, you've looped your network. Probably, eth0 and | |
610 | eth1 are connected to the same physical Ethernet switch. This | |
611 | yields a scenario where OVS receives a broadcast packet on eth0 and | |
612 | sends it out on eth1, then the physical switch connected to eth1 | |
613 | sends the packet back on eth0, and so on forever. More complicated | |
614 | scenarios, involving a loop through multiple switches, are possible | |
615 | too. | |
616 | ||
617 | The solution depends on what you are trying to do: | |
618 | ||
619 | - If you added eth0 and eth1 to get higher bandwidth or higher | |
620 | reliability between OVS and your physical Ethernet switch, | |
621 | use a bond. The following commands create br0 and then add | |
622 | eth0 and eth1 as a bond: | |
623 | ||
624 | ovs-vsctl add-br br0 | |
625 | ovs-vsctl add-bond br0 bond0 eth0 eth1 | |
626 | ||
627 | Bonds have tons of configuration options. Please read the | |
628 | documentation on the Port table in ovs-vswitchd.conf.db(5) | |
629 | for all the details. | |
630 | ||
631 | - Perhaps you don't actually need eth0 and eth1 to be on the | |
632 | same bridge. For example, if you simply want to be able to | |
633 | connect each of them to virtual machines, then you can put | |
634 | each of them on a bridge of its own: | |
635 | ||
636 | ovs-vsctl add-br br0 | |
637 | ovs-vsctl add-port br0 eth0 | |
638 | ||
639 | ovs-vsctl add-br br1 | |
640 | ovs-vsctl add-port br1 eth1 | |
641 | ||
642 | and then connect VMs to br0 and br1. (A potential | |
643 | disadvantage is that traffic cannot directly pass between br0 | |
644 | and br1. Instead, it will go out eth0 and come back in eth1, | |
645 | or vice versa.) | |
646 | ||
647 | - If you have a redundant or complex network topology and you | |
648 | want to prevent loops, turn on spanning tree protocol (STP). | |
649 | The following commands create br0, enable STP, and add eth0 | |
650 | and eth1 to the bridge. The order is important because you | |
651 | don't want have to have a loop in your network even | |
652 | transiently: | |
653 | ||
654 | ovs-vsctl add-br br0 | |
655 | ovs-vsctl set bridge br0 stp_enable=true | |
656 | ovs-vsctl add-port br0 eth0 | |
657 | ovs-vsctl add-port br0 eth1 | |
658 | ||
659 | The Open vSwitch implementation of STP is not well tested. | |
660 | Please report any bugs you observe, but if you'd rather avoid | |
661 | acting as a beta tester then another option might be your | |
662 | best shot. | |
663 | ||
664 | Q: I can't seem to use Open vSwitch in a wireless network. | |
665 | ||
666 | A: Wireless base stations generally only allow packets with the source | |
667 | MAC address of NIC that completed the initial handshake. | |
668 | Therefore, without MAC rewriting, only a single device can | |
669 | communicate over a single wireless link. | |
670 | ||
671 | This isn't specific to Open vSwitch, it's enforced by the access | |
672 | point, so the same problems will show up with the Linux bridge or | |
673 | any other way to do bridging. | |
674 | ||
8748ec7b BP |
675 | Q: I can't seem to add my PPP interface to an Open vSwitch bridge. |
676 | ||
677 | A: PPP most commonly carries IP packets, but Open vSwitch works only | |
678 | with Ethernet frames. The correct way to interface PPP to an | |
679 | Ethernet network is usually to use routing instead of switching. | |
680 | ||
5aa75474 BP |
681 | Q: Is there any documentation on the database tables and fields? |
682 | ||
683 | A: Yes. ovs-vswitchd.conf.db(5) is a comprehensive reference. | |
684 | ||
acf60855 JP |
685 | Q: When I run ovs-dpctl I no longer see the bridges I created. Instead, |
686 | I only see a datapath called "ovs-system". How can I see datapath | |
687 | information about a particular bridge? | |
688 | ||
689 | A: In version 1.9.0, OVS switched to using a single datapath that is | |
690 | shared by all bridges of that type. The "ovs-appctl dpif/*" | |
691 | commands provide similar functionality that is scoped by the bridge. | |
692 | ||
004a6249 JG |
693 | Q: I created a GRE port using ovs-vsctl so why can't I send traffic or |
694 | see the port in the datapath? | |
695 | ||
696 | A: On Linux kernels before 3.11, the OVS GRE module and Linux GRE module | |
697 | cannot be loaded at the same time. It is likely that on your system the | |
698 | Linux GRE module is already loaded and blocking OVS (to confirm, check | |
699 | dmesg for errors regarding GRE registration). To fix this, unload all | |
700 | GRE modules that appear in lsmod as well as the OVS kernel module. You | |
701 | can then reload the OVS module following the directions in INSTALL, | |
702 | which will ensure that dependencies are satisfied. | |
703 | ||
c6bbc394 YT |
704 | Q: Open vSwitch does not seem to obey my packet filter rules. |
705 | ||
706 | A: It depends on mechanisms and configurations you want to use. | |
707 | ||
708 | You cannot usefully use typical packet filters, like iptables, on | |
709 | physical Ethernet ports that you add to an Open vSwitch bridge. | |
710 | This is because Open vSwitch captures packets from the interface at | |
711 | a layer lower below where typical packet-filter implementations | |
712 | install their hooks. (This actually applies to any interface of | |
713 | type "system" that you might add to an Open vSwitch bridge.) | |
714 | ||
715 | You can usefully use typical packet filters on Open vSwitch | |
716 | internal ports as they are mostly ordinary interfaces from the point | |
717 | of view of packet filters. | |
718 | ||
719 | For example, suppose you create a bridge br0 and add Ethernet port | |
720 | eth0 to it. Then you can usefully add iptables rules to affect the | |
721 | internal interface br0, but not the physical interface eth0. (br0 | |
722 | is also where you would add an IP address, as discussed elsewhere | |
723 | in the FAQ.) | |
724 | ||
725 | For simple filtering rules, it might be possible to achieve similar | |
726 | results by installing appropriate OpenFlow flows instead. | |
727 | ||
728 | If the use of a particular packet filter setup is essential, Open | |
729 | vSwitch might not be the best choice for you. On Linux, you might | |
730 | want to consider using the Linux Bridge. (This is the only choice if | |
731 | you want to use ebtables rules.) On NetBSD, you might want to | |
732 | consider using the bridge(4) with BRIDGE_IPF option. | |
733 | ||
c483d489 | 734 | |
bceafb63 BP |
735 | Quality of Service (QoS) |
736 | ------------------------ | |
737 | ||
738 | Q: How do I configure Quality of Service (QoS)? | |
739 | ||
740 | A: Suppose that you want to set up bridge br0 connected to physical | |
741 | Ethernet port eth0 (a 1 Gbps device) and virtual machine interfaces | |
742 | vif1.0 and vif2.0, and that you want to limit traffic from vif1.0 | |
743 | to eth0 to 10 Mbps and from vif2.0 to eth0 to 20 Mbps. Then, you | |
744 | could configure the bridge this way: | |
745 | ||
746 | ovs-vsctl -- \ | |
747 | add-br br0 -- \ | |
0dc8b8c2 YT |
748 | add-port br0 eth0 -- \ |
749 | add-port br0 vif1.0 -- set interface vif1.0 ofport_request=5 -- \ | |
750 | add-port br0 vif2.0 -- set interface vif2.0 ofport_request=6 -- \ | |
751 | set port eth0 qos=@newqos -- \ | |
752 | --id=@newqos create qos type=linux-htb \ | |
bceafb63 | 753 | other-config:max-rate=1000000000 \ |
0dc8b8c2 YT |
754 | queues:123=@vif10queue \ |
755 | queues:234=@vif20queue -- \ | |
bceafb63 BP |
756 | --id=@vif10queue create queue other-config:max-rate=10000000 -- \ |
757 | --id=@vif20queue create queue other-config:max-rate=20000000 | |
758 | ||
759 | At this point, bridge br0 is configured with the ports and eth0 is | |
760 | configured with the queues that you need for QoS, but nothing is | |
761 | actually directing packets from vif1.0 or vif2.0 to the queues that | |
762 | we have set up for them. That means that all of the packets to | |
763 | eth0 are going to the "default queue", which is not what we want. | |
764 | ||
765 | We use OpenFlow to direct packets from vif1.0 and vif2.0 to the | |
766 | queues reserved for them: | |
767 | ||
768 | ovs-ofctl add-flow br0 in_port=5,actions=set_queue:123,normal | |
769 | ovs-ofctl add-flow br0 in_port=6,actions=set_queue:234,normal | |
770 | ||
771 | Each of the above flows matches on the input port, sets up the | |
772 | appropriate queue (123 for vif1.0, 234 for vif2.0), and then | |
773 | executes the "normal" action, which performs the same switching | |
774 | that Open vSwitch would have done without any OpenFlow flows being | |
775 | present. (We know that vif1.0 and vif2.0 have OpenFlow port | |
776 | numbers 5 and 6, respectively, because we set their ofport_request | |
777 | columns above. If we had not done that, then we would have needed | |
778 | to find out their port numbers before setting up these flows.) | |
779 | ||
780 | Now traffic going from vif1.0 or vif2.0 to eth0 should be | |
781 | rate-limited. | |
782 | ||
783 | By the way, if you delete the bridge created by the above commands, | |
784 | with: | |
785 | ||
786 | ovs-vsctl del-br br0 | |
787 | ||
788 | then that will leave one unreferenced QoS record and two | |
789 | unreferenced Queue records in the Open vSwich database. One way to | |
790 | clear them out, assuming you don't have other QoS or Queue records | |
791 | that you want to keep, is: | |
792 | ||
793 | ovs-vsctl -- --all destroy QoS -- --all destroy Queue | |
794 | ||
7839bb41 BP |
795 | If you do want to keep some QoS or Queue records, or the Open |
796 | vSwitch you are using is older than version 1.8 (which added the | |
797 | --all option), then you will have to destroy QoS and Queue records | |
798 | individually. | |
799 | ||
bceafb63 BP |
800 | Q: I configured Quality of Service (QoS) in my OpenFlow network by |
801 | adding records to the QoS and Queue table, but the results aren't | |
802 | what I expect. | |
803 | ||
804 | A: Did you install OpenFlow flows that use your queues? This is the | |
805 | primary way to tell Open vSwitch which queues you want to use. If | |
806 | you don't do this, then the default queue will be used, which will | |
807 | probably not have the effect you want. | |
808 | ||
809 | Refer to the previous question for an example. | |
810 | ||
e6d29aa7 BP |
811 | Q: I'd like to take advantage of some QoS feature that Open vSwitch |
812 | doesn't yet support. How do I do that? | |
813 | ||
814 | A: Open vSwitch does not implement QoS itself. Instead, it can | |
815 | configure some, but not all, of the QoS features built into the | |
816 | Linux kernel. If you need some QoS feature that OVS cannot | |
817 | configure itself, then the first step is to figure out whether | |
818 | Linux QoS supports that feature. If it does, then you can submit a | |
819 | patch to support Open vSwitch configuration for that feature, or | |
820 | you can use "tc" directly to configure the feature in Linux. (If | |
821 | Linux QoS doesn't support the feature you want, then first you have | |
822 | to add that support to Linux.) | |
823 | ||
bceafb63 BP |
824 | Q: I configured QoS, correctly, but my measurements show that it isn't |
825 | working as well as I expect. | |
826 | ||
827 | A: With the Linux kernel, the Open vSwitch implementation of QoS has | |
828 | two aspects: | |
829 | ||
830 | - Open vSwitch configures a subset of Linux kernel QoS | |
831 | features, according to what is in OVSDB. It is possible that | |
832 | this code has bugs. If you believe that this is so, then you | |
833 | can configure the Linux traffic control (QoS) stack directly | |
834 | with the "tc" program. If you get better results that way, | |
835 | you can send a detailed bug report to bugs@openvswitch.org. | |
836 | ||
837 | It is certain that Open vSwitch cannot configure every Linux | |
838 | kernel QoS feature. If you need some feature that OVS cannot | |
839 | configure, then you can also use "tc" directly (or add that | |
840 | feature to OVS). | |
841 | ||
842 | - The Open vSwitch implementation of OpenFlow allows flows to | |
843 | be directed to particular queues. This is pretty simple and | |
844 | unlikely to have serious bugs at this point. | |
845 | ||
846 | However, most problems with QoS on Linux are not bugs in Open | |
847 | vSwitch at all. They tend to be either configuration errors | |
848 | (please see the earlier questions in this section) or issues with | |
849 | the traffic control (QoS) stack in Linux. The Open vSwitch | |
850 | developers are not experts on Linux traffic control. We suggest | |
851 | that, if you believe you are encountering a problem with Linux | |
852 | traffic control, that you consult the tc manpages (e.g. tc(8), | |
853 | tc-htb(8), tc-hfsc(8)), web resources (e.g. http://lartc.org/), or | |
854 | mailing lists (e.g. http://vger.kernel.org/vger-lists.html#netdev). | |
855 | ||
733fd270 BP |
856 | Q: Does Open vSwitch support OpenFlow meters? |
857 | ||
858 | A: Since version 2.0, Open vSwitch has OpenFlow protocol support for | |
859 | OpenFlow meters. There is no implementation of meters in the Open | |
860 | vSwitch software switch (neither the kernel-based nor userspace | |
861 | switches). | |
862 | ||
bceafb63 | 863 | |
c483d489 BP |
864 | VLANs |
865 | ----- | |
866 | ||
14481051 BP |
867 | Q: What's a VLAN? |
868 | ||
869 | A: At the simplest level, a VLAN (short for "virtual LAN") is a way to | |
870 | partition a single switch into multiple switches. Suppose, for | |
871 | example, that you have two groups of machines, group A and group B. | |
872 | You want the machines in group A to be able to talk to each other, | |
873 | and you want the machine in group B to be able to talk to each | |
874 | other, but you don't want the machines in group A to be able to | |
875 | talk to the machines in group B. You can do this with two | |
876 | switches, by plugging the machines in group A into one switch and | |
877 | the machines in group B into the other switch. | |
878 | ||
879 | If you only have one switch, then you can use VLANs to do the same | |
880 | thing, by configuring the ports for machines in group A as VLAN | |
881 | "access ports" for one VLAN and the ports for group B as "access | |
882 | ports" for a different VLAN. The switch will only forward packets | |
883 | between ports that are assigned to the same VLAN, so this | |
884 | effectively subdivides your single switch into two independent | |
885 | switches, one for each group of machines. | |
886 | ||
887 | So far we haven't said anything about VLAN headers. With access | |
888 | ports, like we've described so far, no VLAN header is present in | |
889 | the Ethernet frame. This means that the machines (or switches) | |
890 | connected to access ports need not be aware that VLANs are | |
891 | involved, just like in the case where we use two different physical | |
892 | switches. | |
893 | ||
894 | Now suppose that you have a whole bunch of switches in your | |
895 | network, instead of just one, and that some machines in group A are | |
896 | connected directly to both switches 1 and 2. To allow these | |
897 | machines to talk to each other, you could add an access port for | |
898 | group A's VLAN to switch 1 and another to switch 2, and then | |
899 | connect an Ethernet cable between those ports. That works fine, | |
900 | but it doesn't scale well as the number of switches and the number | |
901 | of VLANs increases, because you use up a lot of valuable switch | |
902 | ports just connecting together your VLANs. | |
903 | ||
904 | This is where VLAN headers come in. Instead of using one cable and | |
905 | two ports per VLAN to connect a pair of switches, we configure a | |
906 | port on each switch as a VLAN "trunk port". Packets sent and | |
907 | received on a trunk port carry a VLAN header that says what VLAN | |
908 | the packet belongs to, so that only two ports total are required to | |
909 | connect the switches, regardless of the number of VLANs in use. | |
910 | Normally, only switches (either physical or virtual) are connected | |
911 | to a trunk port, not individual hosts, because individual hosts | |
912 | don't expect to see a VLAN header in the traffic that they receive. | |
913 | ||
914 | None of the above discussion says anything about particular VLAN | |
915 | numbers. This is because VLAN numbers are completely arbitrary. | |
916 | One must only ensure that a given VLAN is numbered consistently | |
917 | throughout a network and that different VLANs are given different | |
918 | numbers. (That said, VLAN 0 is usually synonymous with a packet | |
919 | that has no VLAN header, and VLAN 4095 is reserved.) | |
920 | ||
c483d489 BP |
921 | Q: VLANs don't work. |
922 | ||
923 | A: Many drivers in Linux kernels before version 3.3 had VLAN-related | |
924 | bugs. If you are having problems with VLANs that you suspect to be | |
925 | driver related, then you have several options: | |
926 | ||
927 | - Upgrade to Linux 3.3 or later. | |
928 | ||
929 | - Build and install a fixed version of the particular driver | |
930 | that is causing trouble, if one is available. | |
931 | ||
932 | - Use a NIC whose driver does not have VLAN problems. | |
933 | ||
934 | - Use "VLAN splinters", a feature in Open vSwitch 1.4 and later | |
935 | that works around bugs in kernel drivers. To enable VLAN | |
936 | splinters on interface eth0, use the command: | |
937 | ||
7b287e99 | 938 | ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true |
c483d489 BP |
939 | |
940 | For VLAN splinters to be effective, Open vSwitch must know | |
941 | which VLANs are in use. See the "VLAN splinters" section in | |
942 | the Interface table in ovs-vswitchd.conf.db(5) for details on | |
943 | how Open vSwitch infers in-use VLANs. | |
944 | ||
945 | VLAN splinters increase memory use and reduce performance, so | |
946 | use them only if needed. | |
947 | ||
948 | - Apply the "vlan workaround" patch from the XenServer kernel | |
949 | patch queue, build Open vSwitch against this patched kernel, | |
950 | and then use ovs-vlan-bug-workaround(8) to enable the VLAN | |
951 | workaround for each interface whose driver is buggy. | |
952 | ||
953 | (This is a nontrivial exercise, so this option is included | |
954 | only for completeness.) | |
955 | ||
956 | It is not always easy to tell whether a Linux kernel driver has | |
957 | buggy VLAN support. The ovs-vlan-test(8) and ovs-test(8) utilities | |
958 | can help you test. See their manpages for details. Of the two | |
959 | utilities, ovs-test(8) is newer and more thorough, but | |
960 | ovs-vlan-test(8) may be easier to use. | |
961 | ||
962 | Q: VLANs still don't work. I've tested the driver so I know that it's OK. | |
963 | ||
964 | A: Do you have VLANs enabled on the physical switch that OVS is | |
965 | attached to? Make sure that the port is configured to trunk the | |
966 | VLAN or VLANs that you are using with OVS. | |
967 | ||
968 | Q: Outgoing VLAN-tagged traffic goes through OVS to my physical switch | |
969 | and to its destination host, but OVS seems to drop incoming return | |
970 | traffic. | |
971 | ||
972 | A: It's possible that you have the VLAN configured on your physical | |
973 | switch as the "native" VLAN. In this mode, the switch treats | |
974 | incoming packets either tagged with the native VLAN or untagged as | |
975 | part of the native VLAN. It may also send outgoing packets in the | |
976 | native VLAN without a VLAN tag. | |
977 | ||
978 | If this is the case, you have two choices: | |
979 | ||
980 | - Change the physical switch port configuration to tag packets | |
981 | it forwards to OVS with the native VLAN instead of forwarding | |
982 | them untagged. | |
983 | ||
984 | - Change the OVS configuration for the physical port to a | |
985 | native VLAN mode. For example, the following sets up a | |
986 | bridge with port eth0 in "native-tagged" mode in VLAN 9: | |
987 | ||
988 | ovs-vsctl add-br br0 | |
989 | ovs-vsctl add-port br0 eth0 tag=9 vlan_mode=native-tagged | |
990 | ||
991 | In this situation, "native-untagged" mode will probably work | |
992 | equally well. Refer to the documentation for the Port table | |
993 | in ovs-vswitchd.conf.db(5) for more information. | |
994 | ||
8d45e938 BP |
995 | Q: I added a pair of VMs on different VLANs, like this: |
996 | ||
997 | ovs-vsctl add-br br0 | |
998 | ovs-vsctl add-port br0 eth0 | |
999 | ovs-vsctl add-port br0 tap0 tag=9 | |
1000 | ovs-vsctl add-port br0 tap1 tag=10 | |
1001 | ||
1002 | but the VMs can't access each other, the external network, or the | |
1003 | Internet. | |
1004 | ||
1005 | A: It is to be expected that the VMs can't access each other. VLANs | |
1006 | are a means to partition a network. When you configured tap0 and | |
1007 | tap1 as access ports for different VLANs, you indicated that they | |
1008 | should be isolated from each other. | |
1009 | ||
1010 | As for the external network and the Internet, it seems likely that | |
1011 | the machines you are trying to access are not on VLAN 9 (or 10) and | |
1012 | that the Internet is not available on VLAN 9 (or 10). | |
1013 | ||
3c8399a2 BP |
1014 | Q: I added a pair of VMs on the same VLAN, like this: |
1015 | ||
1016 | ovs-vsctl add-br br0 | |
1017 | ovs-vsctl add-port br0 eth0 | |
1018 | ovs-vsctl add-port br0 tap0 tag=9 | |
1019 | ovs-vsctl add-port br0 tap1 tag=9 | |
1020 | ||
1021 | The VMs can access each other, but not the external network or the | |
1022 | Internet. | |
1023 | ||
1024 | A: It seems likely that the machines you are trying to access in the | |
1025 | external network are not on VLAN 9 and that the Internet is not | |
1026 | available on VLAN 9. Also, ensure VLAN 9 is set up as an allowed | |
1027 | trunk VLAN on the upstream switch port to which eth0 is connected. | |
1028 | ||
c483d489 BP |
1029 | Q: Can I configure an IP address on a VLAN? |
1030 | ||
1031 | A: Yes. Use an "internal port" configured as an access port. For | |
1032 | example, the following configures IP address 192.168.0.7 on VLAN 9. | |
1033 | That is, OVS will forward packets from eth0 to 192.168.0.7 only if | |
1034 | they have an 802.1Q header with VLAN 9. Conversely, traffic | |
1035 | forwarded from 192.168.0.7 to eth0 will be tagged with an 802.1Q | |
1036 | header with VLAN 9: | |
1037 | ||
1038 | ovs-vsctl add-br br0 | |
1039 | ovs-vsctl add-port br0 eth0 | |
1040 | ovs-vsctl add-port br0 vlan9 tag=9 -- set interface vlan9 type=internal | |
1041 | ifconfig vlan9 192.168.0.7 | |
1042 | ||
8dc54921 BP |
1043 | See also the following question. |
1044 | ||
1045 | Q: I configured one IP address on VLAN 0 and another on VLAN 9, like | |
1046 | this: | |
1047 | ||
1048 | ovs-vsctl add-br br0 | |
1049 | ovs-vsctl add-port br0 eth0 | |
1050 | ifconfig br0 192.168.0.5 | |
1051 | ovs-vsctl add-port br0 vlan9 tag=9 -- set interface vlan9 type=internal | |
1052 | ifconfig vlan9 192.168.0.9 | |
1053 | ||
1054 | but other hosts that are only on VLAN 0 can reach the IP address | |
1055 | configured on VLAN 9. What's going on? | |
1056 | ||
1057 | A: RFC 1122 section 3.3.4.2 "Multihoming Requirements" describes two | |
1058 | approaches to IP address handling in Internet hosts: | |
1059 | ||
1060 | - In the "Strong ES Model", where an ES is a host ("End | |
1061 | System"), an IP address is primarily associated with a | |
1062 | particular interface. The host discards packets that arrive | |
1063 | on interface A if they are destined for an IP address that is | |
1064 | configured on interface B. The host never sends packets from | |
1065 | interface A using a source address configured on interface B. | |
1066 | ||
1067 | - In the "Weak ES Model", an IP address is primarily associated | |
1068 | with a host. The host accepts packets that arrive on any | |
1069 | interface if they are destined for any of the host's IP | |
1070 | addresses, even if the address is configured on some | |
1071 | interface other than the one on which it arrived. The host | |
1072 | does not restrict itself to sending packets from an IP | |
1073 | address associated with the originating interface. | |
1074 | ||
1075 | Linux uses the weak ES model. That means that when packets | |
1076 | destined to the VLAN 9 IP address arrive on eth0 and are bridged to | |
1077 | br0, the kernel IP stack accepts them there for the VLAN 9 IP | |
1078 | address, even though they were not received on vlan9, the network | |
1079 | device for vlan9. | |
1080 | ||
1081 | To simulate the strong ES model on Linux, one may add iptables rule | |
1082 | to filter packets based on source and destination address and | |
1083 | adjust ARP configuration with sysctls. | |
1084 | ||
1085 | BSD uses the strong ES model. | |
1086 | ||
c483d489 BP |
1087 | Q: My OpenFlow controller doesn't see the VLANs that I expect. |
1088 | ||
1089 | A: The configuration for VLANs in the Open vSwitch database (e.g. via | |
1090 | ovs-vsctl) only affects traffic that goes through Open vSwitch's | |
1091 | implementation of the OpenFlow "normal switching" action. By | |
1092 | default, when Open vSwitch isn't connected to a controller and | |
1093 | nothing has been manually configured in the flow table, all traffic | |
1094 | goes through the "normal switching" action. But, if you set up | |
1095 | OpenFlow flows on your own, through a controller or using ovs-ofctl | |
1096 | or through other means, then you have to implement VLAN handling | |
1097 | yourself. | |
1098 | ||
1099 | You can use "normal switching" as a component of your OpenFlow | |
1100 | actions, e.g. by putting "normal" into the lists of actions on | |
1101 | ovs-ofctl or by outputting to OFPP_NORMAL from an OpenFlow | |
241241f5 BP |
1102 | controller. In situations where this is not suitable, you can |
1103 | implement VLAN handling yourself, e.g.: | |
1104 | ||
1105 | - If a packet comes in on an access port, and the flow table | |
1106 | needs to send it out on a trunk port, then the flow can add | |
1107 | the appropriate VLAN tag with the "mod_vlan_vid" action. | |
1108 | ||
1109 | - If a packet comes in on a trunk port, and the flow table | |
1110 | needs to send it out on an access port, then the flow can | |
1111 | strip the VLAN tag with the "strip_vlan" action. | |
c483d489 | 1112 | |
f0a0c1a6 BP |
1113 | Q: I configured ports on a bridge as access ports with different VLAN |
1114 | tags, like this: | |
1115 | ||
1116 | ovs-vsctl add-br br0 | |
1117 | ovs-vsctl set-controller br0 tcp:192.168.0.10:6633 | |
1118 | ovs-vsctl add-port br0 eth0 | |
1119 | ovs-vsctl add-port br0 tap0 tag=9 | |
1120 | ovs-vsctl add-port br0 tap1 tag=10 | |
1121 | ||
1122 | but the VMs running behind tap0 and tap1 can still communicate, | |
1123 | that is, they are not isolated from each other even though they are | |
1124 | on different VLANs. | |
1125 | ||
1126 | A: Do you have a controller configured on br0 (as the commands above | |
1127 | do)? If so, then this is a variant on the previous question, "My | |
1128 | OpenFlow controller doesn't see the VLANs that I expect," and you | |
1129 | can refer to the answer there for more information. | |
1130 | ||
f8003b53 YT |
1131 | Q: How MAC learning works with VLANs? |
1132 | ||
1133 | A: Open vSwitch implements Independent VLAN Learning (IVL) for | |
1134 | OFPP_NORMAL action. I.e. it logically has separate learning tables | |
1135 | for each VLANs. | |
1136 | ||
c483d489 | 1137 | |
0edbe3fb KM |
1138 | VXLANs |
1139 | ----- | |
1140 | ||
1141 | Q: What's a VXLAN? | |
1142 | ||
1143 | A: VXLAN stands for Virtual eXtensible Local Area Network, and is a means | |
1144 | to solve the scaling challenges of VLAN networks in a multi-tenant | |
1145 | environment. VXLAN is an overlay network which transports an L2 network | |
1146 | over an existing L3 network. For more information on VXLAN, please see | |
1147 | the IETF draft available here: | |
1148 | ||
1149 | http://tools.ietf.org/html/draft-mahalingam-dutt-dcops-vxlan-03 | |
1150 | ||
1151 | Q: How much of the VXLAN protocol does Open vSwitch currently support? | |
1152 | ||
1153 | A: Open vSwitch currently supports the framing format for packets on the | |
1154 | wire. There is currently no support for the multicast aspects of VXLAN. | |
1155 | To get around the lack of multicast support, it is possible to | |
1156 | pre-provision MAC to IP address mappings either manually or from a | |
1157 | controller. | |
1158 | ||
1159 | Q: What destination UDP port does the VXLAN implementation in Open vSwitch | |
1160 | use? | |
1161 | ||
1162 | A: By default, Open vSwitch will use the assigned IANA port for VXLAN, which | |
1163 | is 4789. However, it is possible to configure the destination UDP port | |
1164 | manually on a per-VXLAN tunnel basis. An example of this configuration is | |
1165 | provided below. | |
1166 | ||
1167 | ovs-vsctl add-br br0 | |
1168 | ovs-vsctl add-port br0 vxlan1 -- set interface vxlan1 | |
1169 | type=vxlan options:remote_ip=192.168.1.2 options:key=flow | |
1170 | options:dst_port=8472 | |
1171 | ||
1172 | ||
0f5edef0 BP |
1173 | Using OpenFlow (Manually or Via Controller) |
1174 | ------------------------------------------- | |
c483d489 | 1175 | |
7b287e99 JP |
1176 | Q: What versions of OpenFlow does Open vSwitch support? |
1177 | ||
c37c0382 AC |
1178 | A: The following table lists the versions of OpenFlow supported by |
1179 | each version of Open vSwitch: | |
7b287e99 | 1180 | |
42dccab5 BP |
1181 | Open vSwitch OF1.0 OF1.1 OF1.2 OF1.3 OF1.4 OF1.5 |
1182 | =============== ===== ===== ===== ===== ===== ===== | |
1183 | 1.9 and earlier yes --- --- --- --- --- | |
1184 | 1.10 yes --- [*] [*] --- --- | |
1185 | 1.11 yes --- [*] [*] --- --- | |
1186 | 2.0 yes [*] [*] [*] --- --- | |
1187 | 2.1 yes [*] [*] [*] --- --- | |
1188 | 2.2 yes [*] [*] [*] [%] [*] | |
1189 | 2.3 yes yes yes yes [*] [*] | |
8e70e196 | 1190 | |
c37c0382 | 1191 | [*] Supported, with one or more missing features. |
aa233d57 | 1192 | [%] Experimental, unsafe implementation. |
8e70e196 | 1193 | |
6dc53744 BP |
1194 | Open vSwitch 2.3 enables OpenFlow 1.0, 1.1, 1.2, and 1.3 by default |
1195 | in ovs-vswitchd. In Open vSwitch 1.10 through 2.2, OpenFlow 1.1, | |
aa233d57 | 1196 | 1.2, and 1.3 must be enabled manually in ovs-vswitchd. OpenFlow |
42dccab5 BP |
1197 | 1.4 and 1.5 are also supported, with missing features, in Open |
1198 | vSwitch 2.3 and later, but not enabled by default. In any case, | |
1199 | the user may override the default: | |
75fa58f8 | 1200 | |
6dc53744 | 1201 | - To enable OpenFlow 1.0, 1.1, 1.2, and 1.3 on bridge br0: |
75fa58f8 | 1202 | |
6dc53744 BP |
1203 | ovs-vsctl set bridge br0 protocols=OpenFlow10,OpenFlow11,OpenFlow12,OpenFlow13 |
1204 | ||
42dccab5 | 1205 | - To enable OpenFlow 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5 on bridge br0: |
aa233d57 | 1206 | |
42dccab5 | 1207 | ovs-vsctl set bridge br0 protocols=OpenFlow10,OpenFlow11,OpenFlow12,OpenFlow13,OpenFlow14,OpenFlow15 |
aa233d57 | 1208 | |
6dc53744 BP |
1209 | - To enable only OpenFlow 1.0 on bridge br0: |
1210 | ||
1211 | ovs-vsctl set bridge br0 protocols=OpenFlow10 | |
1212 | ||
1213 | All current versions of ovs-ofctl enable only OpenFlow 1.0 by | |
1214 | default. Use the -O option to enable support for later versions of | |
1215 | OpenFlow in ovs-ofctl. For example: | |
ac12b4cb BP |
1216 | |
1217 | ovs-ofctl -O OpenFlow13 dump-flows br0 | |
1218 | ||
aa233d57 BP |
1219 | (Open vSwitch 2.2 had an experimental implementation of OpenFlow |
1220 | 1.4 that could cause crashes. We don't recommend enabling it.) | |
ecb229be | 1221 | |
c37c0382 | 1222 | OPENFLOW-1.1+ in the Open vSwitch source tree tracks support for |
42dccab5 BP |
1223 | OpenFlow 1.1 and later features. When support for OpenFlow 1.4 and |
1224 | 1.5 is solidly implemented, Open vSwitch will enable those version | |
1225 | by default. Also, the OpenFlow 1.5 specification is still under | |
1226 | development and thus subject to change. | |
7b287e99 | 1227 | |
c78a9ead BP |
1228 | Q: Does Open vSwitch support MPLS? |
1229 | ||
1230 | A: Before version 1.11, Open vSwitch did not support MPLS. That is, | |
1231 | these versions can match on MPLS Ethernet types, but they cannot | |
1232 | match, push, or pop MPLS labels, nor can they look past MPLS labels | |
1233 | into the encapsulated packet. | |
1234 | ||
1235 | Open vSwitch versions 1.11, 2.0, and 2.1 have very minimal support | |
1236 | for MPLS. With the userspace datapath only, these versions can | |
1237 | match, push, or pop a single MPLS label, but they still cannot look | |
1238 | past MPLS labels (even after popping them) into the encapsulated | |
7e6410d2 BP |
1239 | packet. Kernel datapath support is unchanged from earlier |
1240 | versions. | |
c78a9ead BP |
1241 | |
1242 | Open vSwitch version 2.2 will be able to match, push, or pop up to | |
1243 | 3 MPLS labels. Looking past MPLS labels into the encapsulated | |
1244 | packet will still be unsupported. Both userspace and kernel | |
1245 | datapaths will be supported, but MPLS processing always happens in | |
1246 | userspace either way, so kernel datapath performance will be | |
1247 | disappointing. | |
1248 | ||
c483d489 BP |
1249 | Q: I'm getting "error type 45250 code 0". What's that? |
1250 | ||
1251 | A: This is a Open vSwitch extension to OpenFlow error codes. Open | |
1252 | vSwitch uses this extension when it must report an error to an | |
1253 | OpenFlow controller but no standard OpenFlow error code is | |
1254 | suitable. | |
1255 | ||
1256 | Open vSwitch logs the errors that it sends to controllers, so the | |
1257 | easiest thing to do is probably to look at the ovs-vswitchd log to | |
1258 | find out what the error was. | |
1259 | ||
1260 | If you want to dissect the extended error message yourself, the | |
1261 | format is documented in include/openflow/nicira-ext.h in the Open | |
1262 | vSwitch source distribution. The extended error codes are | |
1263 | documented in lib/ofp-errors.h. | |
1264 | ||
1265 | Q1: Some of the traffic that I'd expect my OpenFlow controller to see | |
1266 | doesn't actually appear through the OpenFlow connection, even | |
1267 | though I know that it's going through. | |
1268 | Q2: Some of the OpenFlow flows that my controller sets up don't seem | |
1269 | to apply to certain traffic, especially traffic between OVS and | |
1270 | the controller itself. | |
1271 | ||
1272 | A: By default, Open vSwitch assumes that OpenFlow controllers are | |
1273 | connected "in-band", that is, that the controllers are actually | |
1274 | part of the network that is being controlled. In in-band mode, | |
1275 | Open vSwitch sets up special "hidden" flows to make sure that | |
1276 | traffic can make it back and forth between OVS and the controllers. | |
1277 | These hidden flows are higher priority than any flows that can be | |
1278 | set up through OpenFlow, and they are not visible through normal | |
1279 | OpenFlow flow table dumps. | |
1280 | ||
1281 | Usually, the hidden flows are desirable and helpful, but | |
1282 | occasionally they can cause unexpected behavior. You can view the | |
1283 | full OpenFlow flow table, including hidden flows, on bridge br0 | |
1284 | with the command: | |
1285 | ||
1286 | ovs-appctl bridge/dump-flows br0 | |
1287 | ||
1288 | to help you debug. The hidden flows are those with priorities | |
1289 | greater than 65535 (the maximum priority that can be set with | |
1290 | OpenFlow). | |
1291 | ||
1292 | The DESIGN file at the top level of the Open vSwitch source | |
1293 | distribution describes the in-band model in detail. | |
1294 | ||
1295 | If your controllers are not actually in-band (e.g. they are on | |
1296 | localhost via 127.0.0.1, or on a separate network), then you should | |
1297 | configure your controllers in "out-of-band" mode. If you have one | |
1298 | controller on bridge br0, then you can configure out-of-band mode | |
1299 | on it with: | |
1300 | ||
1301 | ovs-vsctl set controller br0 connection-mode=out-of-band | |
1302 | ||
1303 | Q: I configured all my controllers for out-of-band control mode but | |
1304 | "ovs-appctl bridge/dump-flows" still shows some hidden flows. | |
1305 | ||
1306 | A: You probably have a remote manager configured (e.g. with "ovs-vsctl | |
1307 | set-manager"). By default, Open vSwitch assumes that managers need | |
1308 | in-band rules set up on every bridge. You can disable these rules | |
1309 | on bridge br0 with: | |
1310 | ||
1311 | ovs-vsctl set bridge br0 other-config:disable-in-band=true | |
1312 | ||
1313 | This actually disables in-band control entirely for the bridge, as | |
1314 | if all the bridge's controllers were configured for out-of-band | |
1315 | control. | |
1316 | ||
1317 | Q: My OpenFlow controller doesn't see the VLANs that I expect. | |
1318 | ||
1319 | A: See answer under "VLANs", above. | |
1320 | ||
5cb2356b BP |
1321 | Q: I ran "ovs-ofctl add-flow br0 nw_dst=192.168.0.1,actions=drop" |
1322 | but I got a funny message like this: | |
1323 | ||
1324 | ofp_util|INFO|normalization changed ofp_match, details: | |
1325 | ofp_util|INFO| pre: nw_dst=192.168.0.1 | |
1326 | ofp_util|INFO|post: | |
1327 | ||
1328 | and when I ran "ovs-ofctl dump-flows br0" I saw that my nw_dst | |
1329 | match had disappeared, so that the flow ends up matching every | |
1330 | packet. | |
1331 | ||
1332 | A: The term "normalization" in the log message means that a flow | |
1333 | cannot match on an L3 field without saying what L3 protocol is in | |
1334 | use. The "ovs-ofctl" command above didn't specify an L3 protocol, | |
1335 | so the L3 field match was dropped. | |
1336 | ||
1337 | In this case, the L3 protocol could be IP or ARP. A correct | |
1338 | command for each possibility is, respectively: | |
1339 | ||
1340 | ovs-ofctl add-flow br0 ip,nw_dst=192.168.0.1,actions=drop | |
1341 | ||
1342 | and | |
1343 | ||
1344 | ovs-ofctl add-flow br0 arp,nw_dst=192.168.0.1,actions=drop | |
1345 | ||
1346 | Similarly, a flow cannot match on an L4 field without saying what | |
1347 | L4 protocol is in use. For example, the flow match "tp_src=1234" | |
1348 | is, by itself, meaningless and will be ignored. Instead, to match | |
1349 | TCP source port 1234, write "tcp,tp_src=1234", or to match UDP | |
1350 | source port 1234, write "udp,tp_src=1234". | |
1351 | ||
c5b25863 BP |
1352 | Q: How can I figure out the OpenFlow port number for a given port? |
1353 | ||
1354 | A: The OFPT_FEATURES_REQUEST message requests an OpenFlow switch to | |
1355 | respond with an OFPT_FEATURES_REPLY that, among other information, | |
1356 | includes a mapping between OpenFlow port names and numbers. From a | |
1357 | command prompt, "ovs-ofctl show br0" makes such a request and | |
1358 | prints the response for switch br0. | |
1359 | ||
1360 | The Interface table in the Open vSwitch database also maps OpenFlow | |
1361 | port names to numbers. To print the OpenFlow port number | |
1362 | associated with interface eth0, run: | |
1363 | ||
1364 | ovs-vsctl get Interface eth0 ofport | |
1365 | ||
1366 | You can print the entire mapping with: | |
1367 | ||
1368 | ovs-vsctl -- --columns=name,ofport list Interface | |
1369 | ||
1370 | but the output mixes together interfaces from all bridges in the | |
1371 | database, so it may be confusing if more than one bridge exists. | |
1372 | ||
1373 | In the Open vSwitch database, ofport value -1 means that the | |
1374 | interface could not be created due to an error. (The Open vSwitch | |
1375 | log should indicate the reason.) ofport value [] (the empty set) | |
1376 | means that the interface hasn't been created yet. The latter is | |
1377 | normally an intermittent condition (unless ovs-vswitchd is not | |
1378 | running). | |
7b287e99 | 1379 | |
af1ac4b9 BP |
1380 | Q: I added some flows with my controller or with ovs-ofctl, but when I |
1381 | run "ovs-dpctl dump-flows" I don't see them. | |
1382 | ||
1383 | A: ovs-dpctl queries a kernel datapath, not an OpenFlow switch. It | |
1384 | won't display the information that you want. You want to use | |
1385 | "ovs-ofctl dump-flows" instead. | |
1386 | ||
15d63ed3 BP |
1387 | Q: It looks like each of the interfaces in my bonded port shows up |
1388 | as an individual OpenFlow port. Is that right? | |
1389 | ||
1390 | A: Yes, Open vSwitch makes individual bond interfaces visible as | |
1391 | OpenFlow ports, rather than the bond as a whole. The interfaces | |
1392 | are treated together as a bond for only a few purposes: | |
1393 | ||
1394 | - Sending a packet to the OFPP_NORMAL port. (When an OpenFlow | |
1395 | controller is not configured, this happens implicitly to | |
1396 | every packet.) | |
1397 | ||
15d63ed3 BP |
1398 | - Mirrors configured for output to a bonded port. |
1399 | ||
1400 | It would make a lot of sense for Open vSwitch to present a bond as | |
1401 | a single OpenFlow port. If you want to contribute an | |
1402 | implementation of such a feature, please bring it up on the Open | |
1403 | vSwitch development mailing list at dev@openvswitch.org. | |
1404 | ||
bb955418 BP |
1405 | Q: I have a sophisticated network setup involving Open vSwitch, VMs or |
1406 | multiple hosts, and other components. The behavior isn't what I | |
1407 | expect. Help! | |
1408 | ||
1409 | A: To debug network behavior problems, trace the path of a packet, | |
1410 | hop-by-hop, from its origin in one host to a remote host. If | |
1411 | that's correct, then trace the path of the response packet back to | |
1412 | the origin. | |
1413 | ||
1414 | Usually a simple ICMP echo request and reply ("ping") packet is | |
1415 | good enough. Start by initiating an ongoing "ping" from the origin | |
1416 | host to a remote host. If you are tracking down a connectivity | |
1417 | problem, the "ping" will not display any successful output, but | |
1418 | packets are still being sent. (In this case the packets being sent | |
1419 | are likely ARP rather than ICMP.) | |
1420 | ||
1421 | Tools available for tracing include the following: | |
1422 | ||
1423 | - "tcpdump" and "wireshark" for observing hops across network | |
1424 | devices, such as Open vSwitch internal devices and physical | |
1425 | wires. | |
1426 | ||
1427 | - "ovs-appctl dpif/dump-flows <br>" in Open vSwitch 1.10 and | |
1428 | later or "ovs-dpctl dump-flows <br>" in earlier versions. | |
1429 | These tools allow one to observe the actions being taken on | |
1430 | packets in ongoing flows. | |
1431 | ||
1432 | See ovs-vswitchd(8) for "ovs-appctl dpif/dump-flows" | |
1433 | documentation, ovs-dpctl(8) for "ovs-dpctl dump-flows" | |
1434 | documentation, and "Why are there so many different ways to | |
1435 | dump flows?" above for some background. | |
1436 | ||
1437 | - "ovs-appctl ofproto/trace" to observe the logic behind how | |
1438 | ovs-vswitchd treats packets. See ovs-vswitchd(8) for | |
1439 | documentation. You can out more details about a given flow | |
1440 | that "ovs-dpctl dump-flows" displays, by cutting and pasting | |
1441 | a flow from the output into an "ovs-appctl ofproto/trace" | |
1442 | command. | |
1443 | ||
1444 | - SPAN, RSPAN, and ERSPAN features of physical switches, to | |
1445 | observe what goes on at these physical hops. | |
1446 | ||
1447 | Starting at the origin of a given packet, observe the packet at | |
1448 | each hop in turn. For example, in one plausible scenario, you | |
1449 | might: | |
1450 | ||
1451 | 1. "tcpdump" the "eth" interface through which an ARP egresses | |
1452 | a VM, from inside the VM. | |
1453 | ||
1454 | 2. "tcpdump" the "vif" or "tap" interface through which the ARP | |
1455 | ingresses the host machine. | |
1456 | ||
1457 | 3. Use "ovs-dpctl dump-flows" to spot the ARP flow and observe | |
1458 | the host interface through which the ARP egresses the | |
1459 | physical machine. You may need to use "ovs-dpctl show" to | |
1460 | interpret the port numbers. If the output seems surprising, | |
1461 | you can use "ovs-appctl ofproto/trace" to observe details of | |
1462 | how ovs-vswitchd determined the actions in the "ovs-dpctl | |
1463 | dump-flows" output. | |
1464 | ||
1465 | 4. "tcpdump" the "eth" interface through which the ARP egresses | |
1466 | the physical machine. | |
1467 | ||
1468 | 5. "tcpdump" the "eth" interface through which the ARP | |
1469 | ingresses the physical machine, at the remote host that | |
1470 | receives the ARP. | |
1471 | ||
1472 | 6. Use "ovs-dpctl dump-flows" to spot the ARP flow on the | |
1473 | remote host that receives the ARP and observe the VM "vif" | |
1474 | or "tap" interface to which the flow is directed. Again, | |
1475 | "ovs-dpctl show" and "ovs-appctl ofproto/trace" might help. | |
1476 | ||
1477 | 7. "tcpdump" the "vif" or "tap" interface to which the ARP is | |
1478 | directed. | |
1479 | ||
1480 | 8. "tcpdump" the "eth" interface through which the ARP | |
1481 | ingresses a VM, from inside the VM. | |
1482 | ||
1483 | It is likely that during one of these steps you will figure out the | |
1484 | problem. If not, then follow the ARP reply back to the origin, in | |
1485 | reverse. | |
1486 | ||
0f5edef0 BP |
1487 | Q: How do I make a flow drop packets? |
1488 | ||
e5f1da19 BP |
1489 | A: To drop a packet is to receive it without forwarding it. OpenFlow |
1490 | explicitly specifies forwarding actions. Thus, a flow with an | |
1491 | empty set of actions does not forward packets anywhere, causing | |
1492 | them to be dropped. You can specify an empty set of actions with | |
1493 | "actions=" on the ovs-ofctl command line. For example: | |
0f5edef0 BP |
1494 | |
1495 | ovs-ofctl add-flow br0 priority=65535,actions= | |
1496 | ||
1497 | would cause every packet entering switch br0 to be dropped. | |
1498 | ||
1499 | You can write "drop" explicitly if you like. The effect is the | |
1500 | same. Thus, the following command also causes every packet | |
1501 | entering switch br0 to be dropped: | |
1502 | ||
1503 | ovs-ofctl add-flow br0 priority=65535,actions=drop | |
1504 | ||
e5f1da19 BP |
1505 | "drop" is not an action, either in OpenFlow or Open vSwitch. |
1506 | Rather, it is only a way to say that there are no actions. | |
1507 | ||
2fafc091 BP |
1508 | Q: I added a flow to send packets out the ingress port, like this: |
1509 | ||
1510 | ovs-ofctl add-flow br0 in_port=2,actions=2 | |
1511 | ||
1512 | but OVS drops the packets instead. | |
1513 | ||
1514 | A: Yes, OpenFlow requires a switch to ignore attempts to send a packet | |
1515 | out its ingress port. The rationale is that dropping these packets | |
1516 | makes it harder to loop the network. Sometimes this behavior can | |
1517 | even be convenient, e.g. it is often the desired behavior in a flow | |
1518 | that forwards a packet to several ports ("floods" the packet). | |
1519 | ||
6620f928 JS |
1520 | Sometimes one really needs to send a packet out its ingress port |
1521 | ("hairpin"). In this case, output to OFPP_IN_PORT, which in | |
1522 | ovs-ofctl syntax is expressed as just "in_port", e.g.: | |
2fafc091 BP |
1523 | |
1524 | ovs-ofctl add-flow br0 in_port=2,actions=in_port | |
1525 | ||
1526 | This also works in some circumstances where the flow doesn't match | |
1527 | on the input port. For example, if you know that your switch has | |
1528 | five ports numbered 2 through 6, then the following will send every | |
1529 | received packet out every port, even its ingress port: | |
1530 | ||
1531 | ovs-ofctl add-flow br0 actions=2,3,4,5,6,in_port | |
1532 | ||
1533 | or, equivalently: | |
1534 | ||
1535 | ovs-ofctl add-flow br0 actions=all,in_port | |
1536 | ||
1537 | Sometimes, in complicated flow tables with multiple levels of | |
1538 | "resubmit" actions, a flow needs to output to a particular port | |
1539 | that may or may not be the ingress port. It's difficult to take | |
1540 | advantage of OFPP_IN_PORT in this situation. To help, Open vSwitch | |
1541 | provides, as an OpenFlow extension, the ability to modify the | |
1542 | in_port field. Whatever value is currently in the in_port field is | |
1543 | the port to which outputs will be dropped, as well as the | |
1544 | destination for OFPP_IN_PORT. This means that the following will | |
1545 | reliably output to port 2 or to ports 2 through 6, respectively: | |
1546 | ||
1547 | ovs-ofctl add-flow br0 in_port=2,actions=load:0->NXM_OF_IN_PORT[],2 | |
1548 | ovs-ofctl add-flow br0 actions=load:0->NXM_OF_IN_PORT[],2,3,4,5,6 | |
1549 | ||
1550 | If the input port is important, then one may save and restore it on | |
1551 | the stack: | |
1552 | ||
1553 | ovs-ofctl add-flow br0 actions=push:NXM_OF_IN_PORT[],\ | |
1554 | load:0->NXM_OF_IN_PORT[],\ | |
1555 | 2,3,4,5,6,\ | |
1556 | pop:NXM_OF_IN_PORT[] | |
1557 | ||
d4ee72b4 BP |
1558 | Q: My bridge br0 has host 192.168.0.1 on port 1 and host 192.168.0.2 |
1559 | on port 2. I set up flows to forward only traffic destined to the | |
1560 | other host and drop other traffic, like this: | |
1561 | ||
1562 | priority=5,in_port=1,ip,nw_dst=192.168.0.2,actions=2 | |
1563 | priority=5,in_port=2,ip,nw_dst=192.168.0.1,actions=1 | |
1564 | priority=0,actions=drop | |
1565 | ||
1566 | But it doesn't work--I don't get any connectivity when I do this. | |
1567 | Why? | |
1568 | ||
1569 | A: These flows drop the ARP packets that IP hosts use to establish IP | |
1570 | connectivity over Ethernet. To solve the problem, add flows to | |
1571 | allow ARP to pass between the hosts: | |
1572 | ||
1573 | priority=5,in_port=1,arp,actions=2 | |
1574 | priority=5,in_port=2,arp,actions=1 | |
1575 | ||
1576 | This issue can manifest other ways, too. The following flows that | |
1577 | match on Ethernet addresses instead of IP addresses will also drop | |
1578 | ARP packets, because ARP requests are broadcast instead of being | |
1579 | directed to a specific host: | |
1580 | ||
1581 | priority=5,in_port=1,dl_dst=54:00:00:00:00:02,actions=2 | |
1582 | priority=5,in_port=2,dl_dst=54:00:00:00:00:01,actions=1 | |
1583 | priority=0,actions=drop | |
1584 | ||
1585 | The solution already described above will also work in this case. | |
1586 | It may be better to add flows to allow all multicast and broadcast | |
1587 | traffic: | |
1588 | ||
1589 | priority=5,in_port=1,dl_dst=01:00:00:00:00:00/01:00:00:00:00:00,actions=2 | |
1590 | priority=5,in_port=2,dl_dst=01:00:00:00:00:00/01:00:00:00:00:00,actions=1 | |
0f5edef0 | 1591 | |
9a7a9154 YT |
1592 | Q: My bridge disconnects from my controller on add-port/del-port. |
1593 | ||
1594 | A: Reconfiguring your bridge can change your bridge's datapath-id because | |
1595 | Open vSwitch generates datapath-id from the MAC address of one of its ports. | |
1596 | In that case, Open vSwitch disconnects from controllers because there's | |
1597 | no graceful way to notify controllers about the change of datapath-id. | |
1598 | ||
1599 | To avoid the behaviour, you can configure datapath-id manually. | |
1600 | ||
1601 | ovs-vsctl set bridge br0 other-config:datapath-id=0123456789abcdef | |
1602 | ||
66679738 BP |
1603 | |
1604 | Development | |
1605 | ----------- | |
1606 | ||
1607 | Q: How do I implement a new OpenFlow message? | |
1608 | ||
1609 | A: Add your new message to "enum ofpraw" and "enum ofptype" in | |
1610 | lib/ofp-msgs.h, following the existing pattern. Then recompile and | |
1611 | fix all of the new warnings, implementing new functionality for the | |
1612 | new message as needed. (If you configure with --enable-Werror, as | |
1613 | described in INSTALL, then it is impossible to miss any warnings.) | |
1614 | ||
1615 | If you need to add an OpenFlow vendor extension message for a | |
1616 | vendor that doesn't yet have any extension messages, then you will | |
1617 | also need to edit build-aux/extract-ofp-msgs. | |
1618 | ||
1619 | ||
c483d489 BP |
1620 | Contact |
1621 | ------- | |
1622 | ||
1623 | bugs@openvswitch.org | |
1624 | http://openvswitch.org/ |