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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 | ||
7b287e99 JP |
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. | |
3fc7dc18 JP |
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 | ||
3fc7dc18 JP |
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 | |
7b287e99 JP |
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 |
54af97ad | 151 | 2.1.x 2.6.32 to 3.11 |
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152 | |
153 | Open vSwitch userspace should also work with the Linux kernel module | |
154 | built into Linux 3.3 and later. | |
155 | ||
156 | Open vSwitch userspace is not sensitive to the Linux kernel version. | |
37418c86 | 157 | It should build against almost any kernel, certainly against 2.6.32 |
314e60e1 BP |
158 | and later. |
159 | ||
29089a54 RL |
160 | Q: What Linux kernel versions does IPFIX flow monitoring work with? |
161 | ||
162 | A: IPFIX flow monitoring requires the Linux kernel module from Open | |
163 | vSwitch version 1.10.90 or later. | |
164 | ||
33cec590 JG |
165 | Q: Should userspace or kernel be upgraded first to minimize downtime? |
166 | ||
167 | In general, the Open vSwitch userspace should be used with the | |
168 | kernel version included in the same release or with the version | |
169 | from upstream Linux. However, when upgrading between two releases | |
170 | of Open vSwitch it is best to migrate userspace first to reduce | |
23a0330f | 171 | the possibility of incompatibilities. |
33cec590 | 172 | |
7b287e99 JP |
173 | Q: What features are not available in the Open vSwitch kernel datapath |
174 | that ships as part of the upstream Linux kernel? | |
175 | ||
9c333bff JG |
176 | A: The kernel module in upstream Linux does not include support for |
177 | LISP. Work is in progress to add support for LISP to the upstream | |
178 | Linux version of the Open vSwitch kernel module. For now, if you | |
179 | need this feature, use the kernel module from the Open vSwitch | |
0a740f48 EJ |
180 | distribution instead of the upstream Linux kernel module. |
181 | ||
9c333bff JG |
182 | Certain features require kernel support to function or to have |
183 | reasonable performance. If the ovs-vswitchd log file indicates that | |
184 | a feature is not supported, consider upgrading to a newer upstream | |
185 | Linux release or using the kernel module paired with the userspace | |
186 | distribution. | |
6302c641 | 187 | |
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188 | Q: What features are not available when using the userspace datapath? |
189 | ||
0a740f48 | 190 | A: Tunnel virtual ports are not supported, as described in the |
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191 | previous answer. It is also not possible to use queue-related |
192 | actions. On Linux kernels before 2.6.39, maximum-sized VLAN packets | |
193 | may not be transmitted. | |
3fc7dc18 | 194 | |
900dc97c BP |
195 | Q: What happened to the bridge compatibility feature? |
196 | ||
197 | A: Bridge compatibility was a feature of Open vSwitch 1.9 and earlier. | |
198 | When it was enabled, Open vSwitch imitated the interface of the | |
199 | Linux kernel "bridge" module. This allowed users to drop Open | |
200 | vSwitch into environments designed to use the Linux kernel bridge | |
201 | module without adapting the environment to use Open vSwitch. | |
202 | ||
203 | Open vSwitch 1.10 and later do not support bridge compatibility. | |
204 | The feature was dropped because version 1.10 adopted a new internal | |
205 | architecture that made bridge compatibility difficult to maintain. | |
206 | Now that many environments use OVS directly, it would be rarely | |
207 | useful in any case. | |
208 | ||
209 | To use bridge compatibility, install OVS 1.9 or earlier, including | |
210 | the accompanying kernel modules (both the main and bridge | |
211 | compatibility modules), following the instructions that come with | |
212 | the release. Be sure to start the ovs-brcompatd daemon. | |
213 | ||
3fc7dc18 | 214 | |
79aa9fd0 BP |
215 | Terminology |
216 | ----------- | |
217 | ||
218 | Q: I thought Open vSwitch was a virtual Ethernet switch, but the | |
219 | documentation keeps talking about bridges. What's a bridge? | |
220 | ||
221 | A: In networking, the terms "bridge" and "switch" are synonyms. Open | |
222 | vSwitch implements an Ethernet switch, which means that it is also | |
223 | an Ethernet bridge. | |
224 | ||
225 | Q: What's a VLAN? | |
226 | ||
227 | A: See the "VLAN" section below. | |
228 | ||
229 | ||
717e7c8d BP |
230 | Basic Configuration |
231 | ------------------- | |
232 | ||
233 | Q: How do I configure a port as an access port? | |
234 | ||
235 | A: Add "tag=VLAN" to your "ovs-vsctl add-port" command. For example, | |
236 | the following commands configure br0 with eth0 as a trunk port (the | |
237 | default) and tap0 as an access port for VLAN 9: | |
238 | ||
239 | ovs-vsctl add-br br0 | |
240 | ovs-vsctl add-port br0 eth0 | |
241 | ovs-vsctl add-port br0 tap0 tag=9 | |
242 | ||
243 | If you want to configure an already added port as an access port, | |
244 | use "ovs-vsctl set", e.g.: | |
245 | ||
246 | ovs-vsctl set port tap0 tag=9 | |
247 | ||
248 | Q: How do I configure a port as a SPAN port, that is, enable mirroring | |
249 | of all traffic to that port? | |
250 | ||
251 | A: The following commands configure br0 with eth0 and tap0 as trunk | |
252 | ports. All traffic coming in or going out on eth0 or tap0 is also | |
253 | mirrored to tap1; any traffic arriving on tap1 is dropped: | |
254 | ||
255 | ovs-vsctl add-br br0 | |
256 | ovs-vsctl add-port br0 eth0 | |
257 | ovs-vsctl add-port br0 tap0 | |
258 | ovs-vsctl add-port br0 tap1 \ | |
259 | -- --id=@p get port tap1 \ | |
260 | -- --id=@m create mirror name=m0 select-all=true output-port=@p \ | |
261 | -- set bridge br0 mirrors=@m | |
262 | ||
263 | To later disable mirroring, run: | |
264 | ||
265 | ovs-vsctl clear bridge br0 mirrors | |
266 | ||
e253f732 BP |
267 | Q: Does Open vSwitch support configuring a port in promiscuous mode? |
268 | ||
269 | A: Yes. How you configure it depends on what you mean by "promiscuous | |
270 | mode": | |
271 | ||
272 | - Conventionally, "promiscuous mode" is a feature of a network | |
273 | interface card. Ordinarily, a NIC passes to the CPU only the | |
274 | packets actually destined to its host machine. It discards | |
275 | the rest to avoid wasting memory and CPU cycles. When | |
276 | promiscuous mode is enabled, however, it passes every packet | |
277 | to the CPU. On an old-style shared-media or hub-based | |
278 | network, this allows the host to spy on all packets on the | |
279 | network. But in the switched networks that are almost | |
280 | everywhere these days, promiscuous mode doesn't have much | |
281 | effect, because few packets not destined to a host are | |
282 | delivered to the host's NIC. | |
283 | ||
284 | This form of promiscuous mode is configured in the guest OS of | |
285 | the VMs on your bridge, e.g. with "ifconfig". | |
286 | ||
287 | - The VMware vSwitch uses a different definition of "promiscuous | |
288 | mode". When you configure promiscuous mode on a VMware vNIC, | |
289 | the vSwitch sends a copy of every packet received by the | |
290 | vSwitch to that vNIC. That has a much bigger effect than just | |
291 | enabling promiscuous mode in a guest OS. Rather than getting | |
292 | a few stray packets for which the switch does not yet know the | |
293 | correct destination, the vNIC gets every packet. The effect | |
294 | is similar to replacing the vSwitch by a virtual hub. | |
295 | ||
296 | This "promiscuous mode" is what switches normally call "port | |
297 | mirroring" or "SPAN". For information on how to configure | |
298 | SPAN, see "How do I configure a port as a SPAN port, that is, | |
299 | enable mirroring of all traffic to that port?" | |
300 | ||
717e7c8d BP |
301 | Q: How do I configure a VLAN as an RSPAN VLAN, that is, enable |
302 | mirroring of all traffic to that VLAN? | |
303 | ||
304 | A: The following commands configure br0 with eth0 as a trunk port and | |
305 | tap0 as an access port for VLAN 10. All traffic coming in or going | |
306 | out on tap0, as well as traffic coming in or going out on eth0 in | |
307 | VLAN 10, is also mirrored to VLAN 15 on eth0. The original tag for | |
308 | VLAN 10, in cases where one is present, is dropped as part of | |
309 | mirroring: | |
310 | ||
311 | ovs-vsctl add-br br0 | |
312 | ovs-vsctl add-port br0 eth0 | |
313 | ovs-vsctl add-port br0 tap0 tag=10 | |
314 | ovs-vsctl \ | |
315 | -- --id=@m create mirror name=m0 select-all=true select-vlan=10 \ | |
316 | output-vlan=15 \ | |
317 | -- set bridge br0 mirrors=@m | |
318 | ||
319 | To later disable mirroring, run: | |
320 | ||
321 | ovs-vsctl clear bridge br0 mirrors | |
322 | ||
323 | Mirroring to a VLAN can disrupt a network that contains unmanaged | |
324 | switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a | |
325 | GRE tunnel has fewer caveats than mirroring to a VLAN and should | |
326 | generally be preferred. | |
327 | ||
328 | Q: Can I mirror more than one input VLAN to an RSPAN VLAN? | |
329 | ||
330 | A: Yes, but mirroring to a VLAN strips the original VLAN tag in favor | |
331 | of the specified output-vlan. This loss of information may make | |
332 | the mirrored traffic too hard to interpret. | |
333 | ||
334 | To mirror multiple VLANs, use the commands above, but specify a | |
335 | comma-separated list of VLANs as the value for select-vlan. To | |
336 | mirror every VLAN, use the commands above, but omit select-vlan and | |
337 | its value entirely. | |
338 | ||
339 | When a packet arrives on a VLAN that is used as a mirror output | |
340 | VLAN, the mirror is disregarded. Instead, in standalone mode, OVS | |
341 | floods the packet across all the ports for which the mirror output | |
342 | VLAN is configured. (If an OpenFlow controller is in use, then it | |
343 | can override this behavior through the flow table.) If OVS is used | |
344 | as an intermediate switch, rather than an edge switch, this ensures | |
345 | that the RSPAN traffic is distributed through the network. | |
346 | ||
347 | Mirroring to a VLAN can disrupt a network that contains unmanaged | |
348 | switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a | |
349 | GRE tunnel has fewer caveats than mirroring to a VLAN and should | |
350 | generally be preferred. | |
351 | ||
352 | Q: How do I configure mirroring of all traffic to a GRE tunnel? | |
353 | ||
354 | A: The following commands configure br0 with eth0 and tap0 as trunk | |
355 | ports. All traffic coming in or going out on eth0 or tap0 is also | |
356 | mirrored to gre0, a GRE tunnel to the remote host 192.168.1.10; any | |
357 | traffic arriving on gre0 is dropped: | |
358 | ||
359 | ovs-vsctl add-br br0 | |
360 | ovs-vsctl add-port br0 eth0 | |
361 | ovs-vsctl add-port br0 tap0 | |
362 | ovs-vsctl add-port br0 gre0 \ | |
363 | -- set interface gre0 type=gre options:remote_ip=192.168.1.10 \ | |
364 | -- --id=@p get port gre0 \ | |
365 | -- --id=@m create mirror name=m0 select-all=true output-port=@p \ | |
366 | -- set bridge br0 mirrors=@m | |
367 | ||
368 | To later disable mirroring and destroy the GRE tunnel: | |
369 | ||
370 | ovs-vsctl clear bridge br0 mirrors | |
371 | ovs-vcstl del-port br0 gre0 | |
372 | ||
373 | Q: Does Open vSwitch support ERSPAN? | |
374 | ||
375 | A: No. ERSPAN is an undocumented proprietary protocol. As an | |
376 | alternative, Open vSwitch supports mirroring to a GRE tunnel (see | |
377 | above). | |
378 | ||
1ab9712b BP |
379 | Q: How do I connect two bridges? |
380 | ||
381 | A: First, why do you want to do this? Two connected bridges are not | |
382 | much different from a single bridge, so you might as well just have | |
383 | a single bridge with all your ports on it. | |
384 | ||
385 | If you still want to connect two bridges, you can use a pair of | |
386 | patch ports. The following example creates bridges br0 and br1, | |
387 | adds eth0 and tap0 to br0, adds tap1 to br1, and then connects br0 | |
388 | and br1 with a pair of patch ports. | |
389 | ||
390 | ovs-vsctl add-br br0 | |
391 | ovs-vsctl add-port br0 eth0 | |
392 | ovs-vsctl add-port br0 tap0 | |
393 | ovs-vsctl add-br br1 | |
394 | ovs-vsctl add-port br1 tap1 | |
395 | ovs-vsctl \ | |
396 | -- add-port br0 patch0 \ | |
397 | -- set interface patch0 type=patch options:peer=patch1 \ | |
398 | -- add-port br1 patch1 \ | |
399 | -- set interface patch1 type=patch options:peer=patch0 | |
400 | ||
401 | Bridges connected with patch ports are much like a single bridge. | |
402 | For instance, if the example above also added eth1 to br1, and both | |
403 | eth0 and eth1 happened to be connected to the same next-hop switch, | |
404 | then you could loop your network just as you would if you added | |
405 | eth0 and eth1 to the same bridge (see the "Configuration Problems" | |
406 | section below for more information). | |
407 | ||
408 | If you are using Open vSwitch 1.9 or an earlier version, then you | |
409 | need to be using the kernel module bundled with Open vSwitch rather | |
410 | than the one that is integrated into Linux 3.3 and later, because | |
411 | Open vSwitch 1.9 and earlier versions need kernel support for patch | |
412 | ports. This also means that in Open vSwitch 1.9 and earlier, patch | |
413 | ports will not work with the userspace datapath, only with the | |
414 | kernel module. | |
415 | ||
1a274bfe BP |
416 | |
417 | Implementation Details | |
418 | ---------------------- | |
419 | ||
420 | Q: I hear OVS has a couple of kinds of flows. Can you tell me about them? | |
a70fc0cf JP |
421 | |
422 | A: Open vSwitch uses different kinds of flows for different purposes: | |
423 | ||
424 | - OpenFlow flows are the most important kind of flow. OpenFlow | |
425 | controllers use these flows to define a switch's policy. | |
426 | OpenFlow flows support wildcards, priorities, and multiple | |
427 | tables. | |
428 | ||
429 | When in-band control is in use, Open vSwitch sets up a few | |
430 | "hidden" flows, with priority higher than a controller or the | |
431 | user can configure, that are not visible via OpenFlow. (See | |
432 | the "Controller" section of the FAQ for more information | |
433 | about hidden flows.) | |
434 | ||
435 | - The Open vSwitch software switch implementation uses a second | |
d9cb84ff BP |
436 | kind of flow internally. These flows, called "datapath" or |
437 | "kernel" flows, do not support priorities and comprise only a | |
438 | single table, which makes them suitable for caching. (Like | |
439 | OpenFlow flows, datapath flows do support wildcarding, in Open | |
440 | vSwitch 1.11 and later.) OpenFlow flows and datapath flows | |
a70fc0cf JP |
441 | also support different actions and number ports differently. |
442 | ||
d9cb84ff BP |
443 | Datapath flows are an implementation detail that is subject to |
444 | change in future versions of Open vSwitch. Even with the | |
445 | current version of Open vSwitch, hardware switch | |
446 | implementations do not necessarily use this architecture. | |
a70fc0cf | 447 | |
1a274bfe BP |
448 | Users and controllers directly control only the OpenFlow flow |
449 | table. Open vSwitch manages the datapath flow table itself, so | |
450 | users should not normally be concerned with it. | |
451 | ||
452 | Q: Why are there so many different ways to dump flows? | |
453 | ||
454 | A: Open vSwitch has two kinds of flows (see the previous question), so | |
455 | it has commands with different purposes for dumping each kind of | |
456 | flow: | |
a70fc0cf JP |
457 | |
458 | - "ovs-ofctl dump-flows <br>" dumps OpenFlow flows, excluding | |
459 | hidden flows. This is the most commonly useful form of flow | |
460 | dump. (Unlike the other commands, this should work with any | |
461 | OpenFlow switch, not just Open vSwitch.) | |
462 | ||
463 | - "ovs-appctl bridge/dump-flows <br>" dumps OpenFlow flows, | |
464 | including hidden flows. This is occasionally useful for | |
465 | troubleshooting suspected issues with in-band control. | |
466 | ||
d9cb84ff | 467 | - "ovs-dpctl dump-flows [dp]" dumps the datapath flow table |
a70fc0cf | 468 | entries for a Linux kernel-based datapath. In Open vSwitch |
acaaa4b4 BP |
469 | 1.10 and later, ovs-vswitchd merges multiple switches into a |
470 | single datapath, so it will show all the flows on all your | |
471 | kernel-based switches. This command can occasionally be | |
a70fc0cf JP |
472 | useful for debugging. |
473 | ||
474 | - "ovs-appctl dpif/dump-flows <br>", new in Open vSwitch 1.10, | |
d9cb84ff BP |
475 | dumps datapath flows for only the specified bridge, regardless |
476 | of the type. | |
a70fc0cf | 477 | |
717e7c8d | 478 | |
bcb8bde4 JR |
479 | Performance |
480 | ----------- | |
481 | ||
482 | Q: I just upgraded and I see a performance drop. Why? | |
483 | ||
484 | A: The OVS kernel datapath may have been updated to a newer version than | |
485 | the OVS userspace components. Sometimes new versions of OVS kernel | |
486 | module add functionality that is backwards compatible with older | |
487 | userspace components but may cause a drop in performance with them. | |
488 | Especially, if a kernel module from OVS 2.1 or newer is paired with | |
489 | OVS userspace 1.10 or older, there will be a performance drop for | |
490 | TCP traffic. | |
491 | ||
492 | Updating the OVS userspace components to the latest released | |
493 | version should fix the performance degradation. | |
494 | ||
495 | To get the best possible performance and functionality, it is | |
496 | recommended to pair the same versions of the kernel module and OVS | |
497 | userspace. | |
498 | ||
499 | ||
c483d489 BP |
500 | Configuration Problems |
501 | ---------------------- | |
502 | ||
503 | Q: I created a bridge and added my Ethernet port to it, using commands | |
504 | like these: | |
505 | ||
506 | ovs-vsctl add-br br0 | |
507 | ovs-vsctl add-port br0 eth0 | |
508 | ||
509 | and as soon as I ran the "add-port" command I lost all connectivity | |
510 | through eth0. Help! | |
511 | ||
512 | A: A physical Ethernet device that is part of an Open vSwitch bridge | |
513 | should not have an IP address. If one does, then that IP address | |
514 | will not be fully functional. | |
515 | ||
516 | You can restore functionality by moving the IP address to an Open | |
517 | vSwitch "internal" device, such as the network device named after | |
518 | the bridge itself. For example, assuming that eth0's IP address is | |
519 | 192.168.128.5, you could run the commands below to fix up the | |
520 | situation: | |
521 | ||
522 | ifconfig eth0 0.0.0.0 | |
523 | ifconfig br0 192.168.128.5 | |
524 | ||
525 | (If your only connection to the machine running OVS is through the | |
526 | IP address in question, then you would want to run all of these | |
527 | commands on a single command line, or put them into a script.) If | |
528 | there were any additional routes assigned to eth0, then you would | |
529 | also want to use commands to adjust these routes to go through br0. | |
530 | ||
531 | If you use DHCP to obtain an IP address, then you should kill the | |
532 | DHCP client that was listening on the physical Ethernet interface | |
533 | (e.g. eth0) and start one listening on the internal interface | |
534 | (e.g. br0). You might still need to manually clear the IP address | |
535 | from the physical interface (e.g. with "ifconfig eth0 0.0.0.0"). | |
536 | ||
537 | There is no compelling reason why Open vSwitch must work this way. | |
538 | However, this is the way that the Linux kernel bridge module has | |
539 | always worked, so it's a model that those accustomed to Linux | |
540 | bridging are already used to. Also, the model that most people | |
541 | expect is not implementable without kernel changes on all the | |
542 | versions of Linux that Open vSwitch supports. | |
543 | ||
544 | By the way, this issue is not specific to physical Ethernet | |
545 | devices. It applies to all network devices except Open vswitch | |
546 | "internal" devices. | |
547 | ||
548 | Q: I created a bridge and added a couple of Ethernet ports to it, | |
549 | using commands like these: | |
550 | ||
551 | ovs-vsctl add-br br0 | |
552 | ovs-vsctl add-port br0 eth0 | |
553 | ovs-vsctl add-port br0 eth1 | |
554 | ||
555 | and now my network seems to have melted: connectivity is unreliable | |
556 | (even connectivity that doesn't go through Open vSwitch), all the | |
629a6b48 BP |
557 | LEDs on my physical switches are blinking, wireshark shows |
558 | duplicated packets, and CPU usage is very high. | |
c483d489 BP |
559 | |
560 | A: More than likely, you've looped your network. Probably, eth0 and | |
561 | eth1 are connected to the same physical Ethernet switch. This | |
562 | yields a scenario where OVS receives a broadcast packet on eth0 and | |
563 | sends it out on eth1, then the physical switch connected to eth1 | |
564 | sends the packet back on eth0, and so on forever. More complicated | |
565 | scenarios, involving a loop through multiple switches, are possible | |
566 | too. | |
567 | ||
568 | The solution depends on what you are trying to do: | |
569 | ||
570 | - If you added eth0 and eth1 to get higher bandwidth or higher | |
571 | reliability between OVS and your physical Ethernet switch, | |
572 | use a bond. The following commands create br0 and then add | |
573 | eth0 and eth1 as a bond: | |
574 | ||
575 | ovs-vsctl add-br br0 | |
576 | ovs-vsctl add-bond br0 bond0 eth0 eth1 | |
577 | ||
578 | Bonds have tons of configuration options. Please read the | |
579 | documentation on the Port table in ovs-vswitchd.conf.db(5) | |
580 | for all the details. | |
581 | ||
582 | - Perhaps you don't actually need eth0 and eth1 to be on the | |
583 | same bridge. For example, if you simply want to be able to | |
584 | connect each of them to virtual machines, then you can put | |
585 | each of them on a bridge of its own: | |
586 | ||
587 | ovs-vsctl add-br br0 | |
588 | ovs-vsctl add-port br0 eth0 | |
589 | ||
590 | ovs-vsctl add-br br1 | |
591 | ovs-vsctl add-port br1 eth1 | |
592 | ||
593 | and then connect VMs to br0 and br1. (A potential | |
594 | disadvantage is that traffic cannot directly pass between br0 | |
595 | and br1. Instead, it will go out eth0 and come back in eth1, | |
596 | or vice versa.) | |
597 | ||
598 | - If you have a redundant or complex network topology and you | |
599 | want to prevent loops, turn on spanning tree protocol (STP). | |
600 | The following commands create br0, enable STP, and add eth0 | |
601 | and eth1 to the bridge. The order is important because you | |
602 | don't want have to have a loop in your network even | |
603 | transiently: | |
604 | ||
605 | ovs-vsctl add-br br0 | |
606 | ovs-vsctl set bridge br0 stp_enable=true | |
607 | ovs-vsctl add-port br0 eth0 | |
608 | ovs-vsctl add-port br0 eth1 | |
609 | ||
610 | The Open vSwitch implementation of STP is not well tested. | |
611 | Please report any bugs you observe, but if you'd rather avoid | |
612 | acting as a beta tester then another option might be your | |
613 | best shot. | |
614 | ||
615 | Q: I can't seem to use Open vSwitch in a wireless network. | |
616 | ||
617 | A: Wireless base stations generally only allow packets with the source | |
618 | MAC address of NIC that completed the initial handshake. | |
619 | Therefore, without MAC rewriting, only a single device can | |
620 | communicate over a single wireless link. | |
621 | ||
622 | This isn't specific to Open vSwitch, it's enforced by the access | |
623 | point, so the same problems will show up with the Linux bridge or | |
624 | any other way to do bridging. | |
625 | ||
8748ec7b BP |
626 | Q: I can't seem to add my PPP interface to an Open vSwitch bridge. |
627 | ||
628 | A: PPP most commonly carries IP packets, but Open vSwitch works only | |
629 | with Ethernet frames. The correct way to interface PPP to an | |
630 | Ethernet network is usually to use routing instead of switching. | |
631 | ||
5aa75474 BP |
632 | Q: Is there any documentation on the database tables and fields? |
633 | ||
634 | A: Yes. ovs-vswitchd.conf.db(5) is a comprehensive reference. | |
635 | ||
acf60855 JP |
636 | Q: When I run ovs-dpctl I no longer see the bridges I created. Instead, |
637 | I only see a datapath called "ovs-system". How can I see datapath | |
638 | information about a particular bridge? | |
639 | ||
640 | A: In version 1.9.0, OVS switched to using a single datapath that is | |
641 | shared by all bridges of that type. The "ovs-appctl dpif/*" | |
642 | commands provide similar functionality that is scoped by the bridge. | |
643 | ||
004a6249 JG |
644 | Q: I created a GRE port using ovs-vsctl so why can't I send traffic or |
645 | see the port in the datapath? | |
646 | ||
647 | A: On Linux kernels before 3.11, the OVS GRE module and Linux GRE module | |
648 | cannot be loaded at the same time. It is likely that on your system the | |
649 | Linux GRE module is already loaded and blocking OVS (to confirm, check | |
650 | dmesg for errors regarding GRE registration). To fix this, unload all | |
651 | GRE modules that appear in lsmod as well as the OVS kernel module. You | |
652 | can then reload the OVS module following the directions in INSTALL, | |
653 | which will ensure that dependencies are satisfied. | |
654 | ||
c483d489 | 655 | |
bceafb63 BP |
656 | Quality of Service (QoS) |
657 | ------------------------ | |
658 | ||
659 | Q: How do I configure Quality of Service (QoS)? | |
660 | ||
661 | A: Suppose that you want to set up bridge br0 connected to physical | |
662 | Ethernet port eth0 (a 1 Gbps device) and virtual machine interfaces | |
663 | vif1.0 and vif2.0, and that you want to limit traffic from vif1.0 | |
664 | to eth0 to 10 Mbps and from vif2.0 to eth0 to 20 Mbps. Then, you | |
665 | could configure the bridge this way: | |
666 | ||
667 | ovs-vsctl -- \ | |
668 | add-br br0 -- \ | |
669 | add-port br0 eth0 -- \ | |
670 | add-port br0 vif1.0 -- set interface vif1.0 ofport_request=5 -- \ | |
671 | add-port br0 vif2.0 -- set interface vif2.0 ofport_request=6 -- \ | |
672 | set port eth0 qos=@newqos -- \ | |
673 | --id=@newqos create qos type=linux-htb \ | |
674 | other-config:max-rate=1000000000 \ | |
675 | queues:123=@vif10queue \ | |
676 | queues:234=@vif20queue -- \ | |
677 | --id=@vif10queue create queue other-config:max-rate=10000000 -- \ | |
678 | --id=@vif20queue create queue other-config:max-rate=20000000 | |
679 | ||
680 | At this point, bridge br0 is configured with the ports and eth0 is | |
681 | configured with the queues that you need for QoS, but nothing is | |
682 | actually directing packets from vif1.0 or vif2.0 to the queues that | |
683 | we have set up for them. That means that all of the packets to | |
684 | eth0 are going to the "default queue", which is not what we want. | |
685 | ||
686 | We use OpenFlow to direct packets from vif1.0 and vif2.0 to the | |
687 | queues reserved for them: | |
688 | ||
689 | ovs-ofctl add-flow br0 in_port=5,actions=set_queue:123,normal | |
690 | ovs-ofctl add-flow br0 in_port=6,actions=set_queue:234,normal | |
691 | ||
692 | Each of the above flows matches on the input port, sets up the | |
693 | appropriate queue (123 for vif1.0, 234 for vif2.0), and then | |
694 | executes the "normal" action, which performs the same switching | |
695 | that Open vSwitch would have done without any OpenFlow flows being | |
696 | present. (We know that vif1.0 and vif2.0 have OpenFlow port | |
697 | numbers 5 and 6, respectively, because we set their ofport_request | |
698 | columns above. If we had not done that, then we would have needed | |
699 | to find out their port numbers before setting up these flows.) | |
700 | ||
701 | Now traffic going from vif1.0 or vif2.0 to eth0 should be | |
702 | rate-limited. | |
703 | ||
704 | By the way, if you delete the bridge created by the above commands, | |
705 | with: | |
706 | ||
707 | ovs-vsctl del-br br0 | |
708 | ||
709 | then that will leave one unreferenced QoS record and two | |
710 | unreferenced Queue records in the Open vSwich database. One way to | |
711 | clear them out, assuming you don't have other QoS or Queue records | |
712 | that you want to keep, is: | |
713 | ||
714 | ovs-vsctl -- --all destroy QoS -- --all destroy Queue | |
715 | ||
7839bb41 BP |
716 | If you do want to keep some QoS or Queue records, or the Open |
717 | vSwitch you are using is older than version 1.8 (which added the | |
718 | --all option), then you will have to destroy QoS and Queue records | |
719 | individually. | |
720 | ||
bceafb63 BP |
721 | Q: I configured Quality of Service (QoS) in my OpenFlow network by |
722 | adding records to the QoS and Queue table, but the results aren't | |
723 | what I expect. | |
724 | ||
725 | A: Did you install OpenFlow flows that use your queues? This is the | |
726 | primary way to tell Open vSwitch which queues you want to use. If | |
727 | you don't do this, then the default queue will be used, which will | |
728 | probably not have the effect you want. | |
729 | ||
730 | Refer to the previous question for an example. | |
731 | ||
e6d29aa7 BP |
732 | Q: I'd like to take advantage of some QoS feature that Open vSwitch |
733 | doesn't yet support. How do I do that? | |
734 | ||
735 | A: Open vSwitch does not implement QoS itself. Instead, it can | |
736 | configure some, but not all, of the QoS features built into the | |
737 | Linux kernel. If you need some QoS feature that OVS cannot | |
738 | configure itself, then the first step is to figure out whether | |
739 | Linux QoS supports that feature. If it does, then you can submit a | |
740 | patch to support Open vSwitch configuration for that feature, or | |
741 | you can use "tc" directly to configure the feature in Linux. (If | |
742 | Linux QoS doesn't support the feature you want, then first you have | |
743 | to add that support to Linux.) | |
744 | ||
bceafb63 BP |
745 | Q: I configured QoS, correctly, but my measurements show that it isn't |
746 | working as well as I expect. | |
747 | ||
748 | A: With the Linux kernel, the Open vSwitch implementation of QoS has | |
749 | two aspects: | |
750 | ||
751 | - Open vSwitch configures a subset of Linux kernel QoS | |
752 | features, according to what is in OVSDB. It is possible that | |
753 | this code has bugs. If you believe that this is so, then you | |
754 | can configure the Linux traffic control (QoS) stack directly | |
755 | with the "tc" program. If you get better results that way, | |
756 | you can send a detailed bug report to bugs@openvswitch.org. | |
757 | ||
758 | It is certain that Open vSwitch cannot configure every Linux | |
759 | kernel QoS feature. If you need some feature that OVS cannot | |
760 | configure, then you can also use "tc" directly (or add that | |
761 | feature to OVS). | |
762 | ||
763 | - The Open vSwitch implementation of OpenFlow allows flows to | |
764 | be directed to particular queues. This is pretty simple and | |
765 | unlikely to have serious bugs at this point. | |
766 | ||
767 | However, most problems with QoS on Linux are not bugs in Open | |
768 | vSwitch at all. They tend to be either configuration errors | |
769 | (please see the earlier questions in this section) or issues with | |
770 | the traffic control (QoS) stack in Linux. The Open vSwitch | |
771 | developers are not experts on Linux traffic control. We suggest | |
772 | that, if you believe you are encountering a problem with Linux | |
773 | traffic control, that you consult the tc manpages (e.g. tc(8), | |
774 | tc-htb(8), tc-hfsc(8)), web resources (e.g. http://lartc.org/), or | |
775 | mailing lists (e.g. http://vger.kernel.org/vger-lists.html#netdev). | |
776 | ||
777 | ||
c483d489 BP |
778 | VLANs |
779 | ----- | |
780 | ||
14481051 BP |
781 | Q: What's a VLAN? |
782 | ||
783 | A: At the simplest level, a VLAN (short for "virtual LAN") is a way to | |
784 | partition a single switch into multiple switches. Suppose, for | |
785 | example, that you have two groups of machines, group A and group B. | |
786 | You want the machines in group A to be able to talk to each other, | |
787 | and you want the machine in group B to be able to talk to each | |
788 | other, but you don't want the machines in group A to be able to | |
789 | talk to the machines in group B. You can do this with two | |
790 | switches, by plugging the machines in group A into one switch and | |
791 | the machines in group B into the other switch. | |
792 | ||
793 | If you only have one switch, then you can use VLANs to do the same | |
794 | thing, by configuring the ports for machines in group A as VLAN | |
795 | "access ports" for one VLAN and the ports for group B as "access | |
796 | ports" for a different VLAN. The switch will only forward packets | |
797 | between ports that are assigned to the same VLAN, so this | |
798 | effectively subdivides your single switch into two independent | |
799 | switches, one for each group of machines. | |
800 | ||
801 | So far we haven't said anything about VLAN headers. With access | |
802 | ports, like we've described so far, no VLAN header is present in | |
803 | the Ethernet frame. This means that the machines (or switches) | |
804 | connected to access ports need not be aware that VLANs are | |
805 | involved, just like in the case where we use two different physical | |
806 | switches. | |
807 | ||
808 | Now suppose that you have a whole bunch of switches in your | |
809 | network, instead of just one, and that some machines in group A are | |
810 | connected directly to both switches 1 and 2. To allow these | |
811 | machines to talk to each other, you could add an access port for | |
812 | group A's VLAN to switch 1 and another to switch 2, and then | |
813 | connect an Ethernet cable between those ports. That works fine, | |
814 | but it doesn't scale well as the number of switches and the number | |
815 | of VLANs increases, because you use up a lot of valuable switch | |
816 | ports just connecting together your VLANs. | |
817 | ||
818 | This is where VLAN headers come in. Instead of using one cable and | |
819 | two ports per VLAN to connect a pair of switches, we configure a | |
820 | port on each switch as a VLAN "trunk port". Packets sent and | |
821 | received on a trunk port carry a VLAN header that says what VLAN | |
822 | the packet belongs to, so that only two ports total are required to | |
823 | connect the switches, regardless of the number of VLANs in use. | |
824 | Normally, only switches (either physical or virtual) are connected | |
825 | to a trunk port, not individual hosts, because individual hosts | |
826 | don't expect to see a VLAN header in the traffic that they receive. | |
827 | ||
828 | None of the above discussion says anything about particular VLAN | |
829 | numbers. This is because VLAN numbers are completely arbitrary. | |
830 | One must only ensure that a given VLAN is numbered consistently | |
831 | throughout a network and that different VLANs are given different | |
832 | numbers. (That said, VLAN 0 is usually synonymous with a packet | |
833 | that has no VLAN header, and VLAN 4095 is reserved.) | |
834 | ||
c483d489 BP |
835 | Q: VLANs don't work. |
836 | ||
837 | A: Many drivers in Linux kernels before version 3.3 had VLAN-related | |
838 | bugs. If you are having problems with VLANs that you suspect to be | |
839 | driver related, then you have several options: | |
840 | ||
841 | - Upgrade to Linux 3.3 or later. | |
842 | ||
843 | - Build and install a fixed version of the particular driver | |
844 | that is causing trouble, if one is available. | |
845 | ||
846 | - Use a NIC whose driver does not have VLAN problems. | |
847 | ||
848 | - Use "VLAN splinters", a feature in Open vSwitch 1.4 and later | |
849 | that works around bugs in kernel drivers. To enable VLAN | |
850 | splinters on interface eth0, use the command: | |
851 | ||
7b287e99 | 852 | ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true |
c483d489 BP |
853 | |
854 | For VLAN splinters to be effective, Open vSwitch must know | |
855 | which VLANs are in use. See the "VLAN splinters" section in | |
856 | the Interface table in ovs-vswitchd.conf.db(5) for details on | |
857 | how Open vSwitch infers in-use VLANs. | |
858 | ||
859 | VLAN splinters increase memory use and reduce performance, so | |
860 | use them only if needed. | |
861 | ||
862 | - Apply the "vlan workaround" patch from the XenServer kernel | |
863 | patch queue, build Open vSwitch against this patched kernel, | |
864 | and then use ovs-vlan-bug-workaround(8) to enable the VLAN | |
865 | workaround for each interface whose driver is buggy. | |
866 | ||
867 | (This is a nontrivial exercise, so this option is included | |
868 | only for completeness.) | |
869 | ||
870 | It is not always easy to tell whether a Linux kernel driver has | |
871 | buggy VLAN support. The ovs-vlan-test(8) and ovs-test(8) utilities | |
872 | can help you test. See their manpages for details. Of the two | |
873 | utilities, ovs-test(8) is newer and more thorough, but | |
874 | ovs-vlan-test(8) may be easier to use. | |
875 | ||
876 | Q: VLANs still don't work. I've tested the driver so I know that it's OK. | |
877 | ||
878 | A: Do you have VLANs enabled on the physical switch that OVS is | |
879 | attached to? Make sure that the port is configured to trunk the | |
880 | VLAN or VLANs that you are using with OVS. | |
881 | ||
882 | Q: Outgoing VLAN-tagged traffic goes through OVS to my physical switch | |
883 | and to its destination host, but OVS seems to drop incoming return | |
884 | traffic. | |
885 | ||
886 | A: It's possible that you have the VLAN configured on your physical | |
887 | switch as the "native" VLAN. In this mode, the switch treats | |
888 | incoming packets either tagged with the native VLAN or untagged as | |
889 | part of the native VLAN. It may also send outgoing packets in the | |
890 | native VLAN without a VLAN tag. | |
891 | ||
892 | If this is the case, you have two choices: | |
893 | ||
894 | - Change the physical switch port configuration to tag packets | |
895 | it forwards to OVS with the native VLAN instead of forwarding | |
896 | them untagged. | |
897 | ||
898 | - Change the OVS configuration for the physical port to a | |
899 | native VLAN mode. For example, the following sets up a | |
900 | bridge with port eth0 in "native-tagged" mode in VLAN 9: | |
901 | ||
902 | ovs-vsctl add-br br0 | |
903 | ovs-vsctl add-port br0 eth0 tag=9 vlan_mode=native-tagged | |
904 | ||
905 | In this situation, "native-untagged" mode will probably work | |
906 | equally well. Refer to the documentation for the Port table | |
907 | in ovs-vswitchd.conf.db(5) for more information. | |
908 | ||
8d45e938 BP |
909 | Q: I added a pair of VMs on different VLANs, like this: |
910 | ||
911 | ovs-vsctl add-br br0 | |
912 | ovs-vsctl add-port br0 eth0 | |
913 | ovs-vsctl add-port br0 tap0 tag=9 | |
914 | ovs-vsctl add-port br0 tap1 tag=10 | |
915 | ||
916 | but the VMs can't access each other, the external network, or the | |
917 | Internet. | |
918 | ||
919 | A: It is to be expected that the VMs can't access each other. VLANs | |
920 | are a means to partition a network. When you configured tap0 and | |
921 | tap1 as access ports for different VLANs, you indicated that they | |
922 | should be isolated from each other. | |
923 | ||
924 | As for the external network and the Internet, it seems likely that | |
925 | the machines you are trying to access are not on VLAN 9 (or 10) and | |
926 | that the Internet is not available on VLAN 9 (or 10). | |
927 | ||
3c8399a2 BP |
928 | Q: I added a pair of VMs on the same VLAN, like this: |
929 | ||
930 | ovs-vsctl add-br br0 | |
931 | ovs-vsctl add-port br0 eth0 | |
932 | ovs-vsctl add-port br0 tap0 tag=9 | |
933 | ovs-vsctl add-port br0 tap1 tag=9 | |
934 | ||
935 | The VMs can access each other, but not the external network or the | |
936 | Internet. | |
937 | ||
938 | A: It seems likely that the machines you are trying to access in the | |
939 | external network are not on VLAN 9 and that the Internet is not | |
940 | available on VLAN 9. Also, ensure VLAN 9 is set up as an allowed | |
941 | trunk VLAN on the upstream switch port to which eth0 is connected. | |
942 | ||
c483d489 BP |
943 | Q: Can I configure an IP address on a VLAN? |
944 | ||
945 | A: Yes. Use an "internal port" configured as an access port. For | |
946 | example, the following configures IP address 192.168.0.7 on VLAN 9. | |
947 | That is, OVS will forward packets from eth0 to 192.168.0.7 only if | |
948 | they have an 802.1Q header with VLAN 9. Conversely, traffic | |
949 | forwarded from 192.168.0.7 to eth0 will be tagged with an 802.1Q | |
950 | header with VLAN 9: | |
951 | ||
952 | ovs-vsctl add-br br0 | |
953 | ovs-vsctl add-port br0 eth0 | |
954 | ovs-vsctl add-port br0 vlan9 tag=9 -- set interface vlan9 type=internal | |
955 | ifconfig vlan9 192.168.0.7 | |
956 | ||
8dc54921 BP |
957 | See also the following question. |
958 | ||
959 | Q: I configured one IP address on VLAN 0 and another on VLAN 9, like | |
960 | this: | |
961 | ||
962 | ovs-vsctl add-br br0 | |
963 | ovs-vsctl add-port br0 eth0 | |
964 | ifconfig br0 192.168.0.5 | |
965 | ovs-vsctl add-port br0 vlan9 tag=9 -- set interface vlan9 type=internal | |
966 | ifconfig vlan9 192.168.0.9 | |
967 | ||
968 | but other hosts that are only on VLAN 0 can reach the IP address | |
969 | configured on VLAN 9. What's going on? | |
970 | ||
971 | A: RFC 1122 section 3.3.4.2 "Multihoming Requirements" describes two | |
972 | approaches to IP address handling in Internet hosts: | |
973 | ||
974 | - In the "Strong ES Model", where an ES is a host ("End | |
975 | System"), an IP address is primarily associated with a | |
976 | particular interface. The host discards packets that arrive | |
977 | on interface A if they are destined for an IP address that is | |
978 | configured on interface B. The host never sends packets from | |
979 | interface A using a source address configured on interface B. | |
980 | ||
981 | - In the "Weak ES Model", an IP address is primarily associated | |
982 | with a host. The host accepts packets that arrive on any | |
983 | interface if they are destined for any of the host's IP | |
984 | addresses, even if the address is configured on some | |
985 | interface other than the one on which it arrived. The host | |
986 | does not restrict itself to sending packets from an IP | |
987 | address associated with the originating interface. | |
988 | ||
989 | Linux uses the weak ES model. That means that when packets | |
990 | destined to the VLAN 9 IP address arrive on eth0 and are bridged to | |
991 | br0, the kernel IP stack accepts them there for the VLAN 9 IP | |
992 | address, even though they were not received on vlan9, the network | |
993 | device for vlan9. | |
994 | ||
995 | To simulate the strong ES model on Linux, one may add iptables rule | |
996 | to filter packets based on source and destination address and | |
997 | adjust ARP configuration with sysctls. | |
998 | ||
999 | BSD uses the strong ES model. | |
1000 | ||
c483d489 BP |
1001 | Q: My OpenFlow controller doesn't see the VLANs that I expect. |
1002 | ||
1003 | A: The configuration for VLANs in the Open vSwitch database (e.g. via | |
1004 | ovs-vsctl) only affects traffic that goes through Open vSwitch's | |
1005 | implementation of the OpenFlow "normal switching" action. By | |
1006 | default, when Open vSwitch isn't connected to a controller and | |
1007 | nothing has been manually configured in the flow table, all traffic | |
1008 | goes through the "normal switching" action. But, if you set up | |
1009 | OpenFlow flows on your own, through a controller or using ovs-ofctl | |
1010 | or through other means, then you have to implement VLAN handling | |
1011 | yourself. | |
1012 | ||
1013 | You can use "normal switching" as a component of your OpenFlow | |
1014 | actions, e.g. by putting "normal" into the lists of actions on | |
1015 | ovs-ofctl or by outputting to OFPP_NORMAL from an OpenFlow | |
241241f5 BP |
1016 | controller. In situations where this is not suitable, you can |
1017 | implement VLAN handling yourself, e.g.: | |
1018 | ||
1019 | - If a packet comes in on an access port, and the flow table | |
1020 | needs to send it out on a trunk port, then the flow can add | |
1021 | the appropriate VLAN tag with the "mod_vlan_vid" action. | |
1022 | ||
1023 | - If a packet comes in on a trunk port, and the flow table | |
1024 | needs to send it out on an access port, then the flow can | |
1025 | strip the VLAN tag with the "strip_vlan" action. | |
c483d489 | 1026 | |
f0a0c1a6 BP |
1027 | Q: I configured ports on a bridge as access ports with different VLAN |
1028 | tags, like this: | |
1029 | ||
1030 | ovs-vsctl add-br br0 | |
1031 | ovs-vsctl set-controller br0 tcp:192.168.0.10:6633 | |
1032 | ovs-vsctl add-port br0 eth0 | |
1033 | ovs-vsctl add-port br0 tap0 tag=9 | |
1034 | ovs-vsctl add-port br0 tap1 tag=10 | |
1035 | ||
1036 | but the VMs running behind tap0 and tap1 can still communicate, | |
1037 | that is, they are not isolated from each other even though they are | |
1038 | on different VLANs. | |
1039 | ||
1040 | A: Do you have a controller configured on br0 (as the commands above | |
1041 | do)? If so, then this is a variant on the previous question, "My | |
1042 | OpenFlow controller doesn't see the VLANs that I expect," and you | |
1043 | can refer to the answer there for more information. | |
1044 | ||
c483d489 | 1045 | |
0edbe3fb KM |
1046 | VXLANs |
1047 | ----- | |
1048 | ||
1049 | Q: What's a VXLAN? | |
1050 | ||
1051 | A: VXLAN stands for Virtual eXtensible Local Area Network, and is a means | |
1052 | to solve the scaling challenges of VLAN networks in a multi-tenant | |
1053 | environment. VXLAN is an overlay network which transports an L2 network | |
1054 | over an existing L3 network. For more information on VXLAN, please see | |
1055 | the IETF draft available here: | |
1056 | ||
1057 | http://tools.ietf.org/html/draft-mahalingam-dutt-dcops-vxlan-03 | |
1058 | ||
1059 | Q: How much of the VXLAN protocol does Open vSwitch currently support? | |
1060 | ||
1061 | A: Open vSwitch currently supports the framing format for packets on the | |
1062 | wire. There is currently no support for the multicast aspects of VXLAN. | |
1063 | To get around the lack of multicast support, it is possible to | |
1064 | pre-provision MAC to IP address mappings either manually or from a | |
1065 | controller. | |
1066 | ||
1067 | Q: What destination UDP port does the VXLAN implementation in Open vSwitch | |
1068 | use? | |
1069 | ||
1070 | A: By default, Open vSwitch will use the assigned IANA port for VXLAN, which | |
1071 | is 4789. However, it is possible to configure the destination UDP port | |
1072 | manually on a per-VXLAN tunnel basis. An example of this configuration is | |
1073 | provided below. | |
1074 | ||
1075 | ovs-vsctl add-br br0 | |
1076 | ovs-vsctl add-port br0 vxlan1 -- set interface vxlan1 | |
1077 | type=vxlan options:remote_ip=192.168.1.2 options:key=flow | |
1078 | options:dst_port=8472 | |
1079 | ||
1080 | ||
0f5edef0 BP |
1081 | Using OpenFlow (Manually or Via Controller) |
1082 | ------------------------------------------- | |
c483d489 | 1083 | |
7b287e99 JP |
1084 | Q: What versions of OpenFlow does Open vSwitch support? |
1085 | ||
8e70e196 BP |
1086 | A: Open vSwitch 1.9 and earlier support only OpenFlow 1.0 (plus |
1087 | extensions that bring in many of the features from later versions | |
1088 | of OpenFlow). | |
7b287e99 | 1089 | |
75fa58f8 BP |
1090 | Open vSwitch 1.10 and later have experimental support for OpenFlow |
1091 | 1.2 and 1.3. On these versions of Open vSwitch, the following | |
1092 | command enables OpenFlow 1.0, 1.2, and 1.3 on bridge br0: | |
8e70e196 | 1093 | |
12eadc32 | 1094 | ovs-vsctl set bridge br0 protocols=OpenFlow10,OpenFlow12,OpenFlow13 |
8e70e196 | 1095 | |
ae179b12 | 1096 | Open vSwitch version 2.0 and later will have experimental support |
75fa58f8 BP |
1097 | for OpenFlow 1.1, 1.2, and 1.3. On these versions of Open vSwitch, |
1098 | the following command enables OpenFlow 1.0, 1.1, 1.2, and 1.3 on | |
1099 | bridge br0: | |
1100 | ||
1101 | ovs-vsctl set bridge br0 protocols=OpenFlow10,OpenFlow11,OpenFlow12,OpenFlow13 | |
1102 | ||
ac12b4cb BP |
1103 | Use the -O option to enable support for later versions of OpenFlow |
1104 | in ovs-ofctl. For example: | |
1105 | ||
1106 | ovs-ofctl -O OpenFlow13 dump-flows br0 | |
1107 | ||
75fa58f8 BP |
1108 | Support for OpenFlow 1.1, 1.2, and 1.3 is still incomplete. Work |
1109 | to be done is tracked in OPENFLOW-1.1+ in the Open vSwitch sources | |
8e70e196 BP |
1110 | (also via http://openvswitch.org/development/openflow-1-x-plan/). |
1111 | When support for a given OpenFlow version is solidly implemented, | |
1112 | Open vSwitch will enable that version by default. | |
7b287e99 | 1113 | |
c483d489 BP |
1114 | Q: I'm getting "error type 45250 code 0". What's that? |
1115 | ||
1116 | A: This is a Open vSwitch extension to OpenFlow error codes. Open | |
1117 | vSwitch uses this extension when it must report an error to an | |
1118 | OpenFlow controller but no standard OpenFlow error code is | |
1119 | suitable. | |
1120 | ||
1121 | Open vSwitch logs the errors that it sends to controllers, so the | |
1122 | easiest thing to do is probably to look at the ovs-vswitchd log to | |
1123 | find out what the error was. | |
1124 | ||
1125 | If you want to dissect the extended error message yourself, the | |
1126 | format is documented in include/openflow/nicira-ext.h in the Open | |
1127 | vSwitch source distribution. The extended error codes are | |
1128 | documented in lib/ofp-errors.h. | |
1129 | ||
1130 | Q1: Some of the traffic that I'd expect my OpenFlow controller to see | |
1131 | doesn't actually appear through the OpenFlow connection, even | |
1132 | though I know that it's going through. | |
1133 | Q2: Some of the OpenFlow flows that my controller sets up don't seem | |
1134 | to apply to certain traffic, especially traffic between OVS and | |
1135 | the controller itself. | |
1136 | ||
1137 | A: By default, Open vSwitch assumes that OpenFlow controllers are | |
1138 | connected "in-band", that is, that the controllers are actually | |
1139 | part of the network that is being controlled. In in-band mode, | |
1140 | Open vSwitch sets up special "hidden" flows to make sure that | |
1141 | traffic can make it back and forth between OVS and the controllers. | |
1142 | These hidden flows are higher priority than any flows that can be | |
1143 | set up through OpenFlow, and they are not visible through normal | |
1144 | OpenFlow flow table dumps. | |
1145 | ||
1146 | Usually, the hidden flows are desirable and helpful, but | |
1147 | occasionally they can cause unexpected behavior. You can view the | |
1148 | full OpenFlow flow table, including hidden flows, on bridge br0 | |
1149 | with the command: | |
1150 | ||
1151 | ovs-appctl bridge/dump-flows br0 | |
1152 | ||
1153 | to help you debug. The hidden flows are those with priorities | |
1154 | greater than 65535 (the maximum priority that can be set with | |
1155 | OpenFlow). | |
1156 | ||
1157 | The DESIGN file at the top level of the Open vSwitch source | |
1158 | distribution describes the in-band model in detail. | |
1159 | ||
1160 | If your controllers are not actually in-band (e.g. they are on | |
1161 | localhost via 127.0.0.1, or on a separate network), then you should | |
1162 | configure your controllers in "out-of-band" mode. If you have one | |
1163 | controller on bridge br0, then you can configure out-of-band mode | |
1164 | on it with: | |
1165 | ||
1166 | ovs-vsctl set controller br0 connection-mode=out-of-band | |
1167 | ||
1168 | Q: I configured all my controllers for out-of-band control mode but | |
1169 | "ovs-appctl bridge/dump-flows" still shows some hidden flows. | |
1170 | ||
1171 | A: You probably have a remote manager configured (e.g. with "ovs-vsctl | |
1172 | set-manager"). By default, Open vSwitch assumes that managers need | |
1173 | in-band rules set up on every bridge. You can disable these rules | |
1174 | on bridge br0 with: | |
1175 | ||
1176 | ovs-vsctl set bridge br0 other-config:disable-in-band=true | |
1177 | ||
1178 | This actually disables in-band control entirely for the bridge, as | |
1179 | if all the bridge's controllers were configured for out-of-band | |
1180 | control. | |
1181 | ||
1182 | Q: My OpenFlow controller doesn't see the VLANs that I expect. | |
1183 | ||
1184 | A: See answer under "VLANs", above. | |
1185 | ||
5cb2356b BP |
1186 | Q: I ran "ovs-ofctl add-flow br0 nw_dst=192.168.0.1,actions=drop" |
1187 | but I got a funny message like this: | |
1188 | ||
1189 | ofp_util|INFO|normalization changed ofp_match, details: | |
1190 | ofp_util|INFO| pre: nw_dst=192.168.0.1 | |
1191 | ofp_util|INFO|post: | |
1192 | ||
1193 | and when I ran "ovs-ofctl dump-flows br0" I saw that my nw_dst | |
1194 | match had disappeared, so that the flow ends up matching every | |
1195 | packet. | |
1196 | ||
1197 | A: The term "normalization" in the log message means that a flow | |
1198 | cannot match on an L3 field without saying what L3 protocol is in | |
1199 | use. The "ovs-ofctl" command above didn't specify an L3 protocol, | |
1200 | so the L3 field match was dropped. | |
1201 | ||
1202 | In this case, the L3 protocol could be IP or ARP. A correct | |
1203 | command for each possibility is, respectively: | |
1204 | ||
1205 | ovs-ofctl add-flow br0 ip,nw_dst=192.168.0.1,actions=drop | |
1206 | ||
1207 | and | |
1208 | ||
1209 | ovs-ofctl add-flow br0 arp,nw_dst=192.168.0.1,actions=drop | |
1210 | ||
1211 | Similarly, a flow cannot match on an L4 field without saying what | |
1212 | L4 protocol is in use. For example, the flow match "tp_src=1234" | |
1213 | is, by itself, meaningless and will be ignored. Instead, to match | |
1214 | TCP source port 1234, write "tcp,tp_src=1234", or to match UDP | |
1215 | source port 1234, write "udp,tp_src=1234". | |
1216 | ||
c5b25863 BP |
1217 | Q: How can I figure out the OpenFlow port number for a given port? |
1218 | ||
1219 | A: The OFPT_FEATURES_REQUEST message requests an OpenFlow switch to | |
1220 | respond with an OFPT_FEATURES_REPLY that, among other information, | |
1221 | includes a mapping between OpenFlow port names and numbers. From a | |
1222 | command prompt, "ovs-ofctl show br0" makes such a request and | |
1223 | prints the response for switch br0. | |
1224 | ||
1225 | The Interface table in the Open vSwitch database also maps OpenFlow | |
1226 | port names to numbers. To print the OpenFlow port number | |
1227 | associated with interface eth0, run: | |
1228 | ||
1229 | ovs-vsctl get Interface eth0 ofport | |
1230 | ||
1231 | You can print the entire mapping with: | |
1232 | ||
1233 | ovs-vsctl -- --columns=name,ofport list Interface | |
1234 | ||
1235 | but the output mixes together interfaces from all bridges in the | |
1236 | database, so it may be confusing if more than one bridge exists. | |
1237 | ||
1238 | In the Open vSwitch database, ofport value -1 means that the | |
1239 | interface could not be created due to an error. (The Open vSwitch | |
1240 | log should indicate the reason.) ofport value [] (the empty set) | |
1241 | means that the interface hasn't been created yet. The latter is | |
1242 | normally an intermittent condition (unless ovs-vswitchd is not | |
1243 | running). | |
7b287e99 | 1244 | |
af1ac4b9 BP |
1245 | Q: I added some flows with my controller or with ovs-ofctl, but when I |
1246 | run "ovs-dpctl dump-flows" I don't see them. | |
1247 | ||
1248 | A: ovs-dpctl queries a kernel datapath, not an OpenFlow switch. It | |
1249 | won't display the information that you want. You want to use | |
1250 | "ovs-ofctl dump-flows" instead. | |
1251 | ||
15d63ed3 BP |
1252 | Q: It looks like each of the interfaces in my bonded port shows up |
1253 | as an individual OpenFlow port. Is that right? | |
1254 | ||
1255 | A: Yes, Open vSwitch makes individual bond interfaces visible as | |
1256 | OpenFlow ports, rather than the bond as a whole. The interfaces | |
1257 | are treated together as a bond for only a few purposes: | |
1258 | ||
1259 | - Sending a packet to the OFPP_NORMAL port. (When an OpenFlow | |
1260 | controller is not configured, this happens implicitly to | |
1261 | every packet.) | |
1262 | ||
15d63ed3 BP |
1263 | - Mirrors configured for output to a bonded port. |
1264 | ||
1265 | It would make a lot of sense for Open vSwitch to present a bond as | |
1266 | a single OpenFlow port. If you want to contribute an | |
1267 | implementation of such a feature, please bring it up on the Open | |
1268 | vSwitch development mailing list at dev@openvswitch.org. | |
1269 | ||
bb955418 BP |
1270 | Q: I have a sophisticated network setup involving Open vSwitch, VMs or |
1271 | multiple hosts, and other components. The behavior isn't what I | |
1272 | expect. Help! | |
1273 | ||
1274 | A: To debug network behavior problems, trace the path of a packet, | |
1275 | hop-by-hop, from its origin in one host to a remote host. If | |
1276 | that's correct, then trace the path of the response packet back to | |
1277 | the origin. | |
1278 | ||
1279 | Usually a simple ICMP echo request and reply ("ping") packet is | |
1280 | good enough. Start by initiating an ongoing "ping" from the origin | |
1281 | host to a remote host. If you are tracking down a connectivity | |
1282 | problem, the "ping" will not display any successful output, but | |
1283 | packets are still being sent. (In this case the packets being sent | |
1284 | are likely ARP rather than ICMP.) | |
1285 | ||
1286 | Tools available for tracing include the following: | |
1287 | ||
1288 | - "tcpdump" and "wireshark" for observing hops across network | |
1289 | devices, such as Open vSwitch internal devices and physical | |
1290 | wires. | |
1291 | ||
1292 | - "ovs-appctl dpif/dump-flows <br>" in Open vSwitch 1.10 and | |
1293 | later or "ovs-dpctl dump-flows <br>" in earlier versions. | |
1294 | These tools allow one to observe the actions being taken on | |
1295 | packets in ongoing flows. | |
1296 | ||
1297 | See ovs-vswitchd(8) for "ovs-appctl dpif/dump-flows" | |
1298 | documentation, ovs-dpctl(8) for "ovs-dpctl dump-flows" | |
1299 | documentation, and "Why are there so many different ways to | |
1300 | dump flows?" above for some background. | |
1301 | ||
1302 | - "ovs-appctl ofproto/trace" to observe the logic behind how | |
1303 | ovs-vswitchd treats packets. See ovs-vswitchd(8) for | |
1304 | documentation. You can out more details about a given flow | |
1305 | that "ovs-dpctl dump-flows" displays, by cutting and pasting | |
1306 | a flow from the output into an "ovs-appctl ofproto/trace" | |
1307 | command. | |
1308 | ||
1309 | - SPAN, RSPAN, and ERSPAN features of physical switches, to | |
1310 | observe what goes on at these physical hops. | |
1311 | ||
1312 | Starting at the origin of a given packet, observe the packet at | |
1313 | each hop in turn. For example, in one plausible scenario, you | |
1314 | might: | |
1315 | ||
1316 | 1. "tcpdump" the "eth" interface through which an ARP egresses | |
1317 | a VM, from inside the VM. | |
1318 | ||
1319 | 2. "tcpdump" the "vif" or "tap" interface through which the ARP | |
1320 | ingresses the host machine. | |
1321 | ||
1322 | 3. Use "ovs-dpctl dump-flows" to spot the ARP flow and observe | |
1323 | the host interface through which the ARP egresses the | |
1324 | physical machine. You may need to use "ovs-dpctl show" to | |
1325 | interpret the port numbers. If the output seems surprising, | |
1326 | you can use "ovs-appctl ofproto/trace" to observe details of | |
1327 | how ovs-vswitchd determined the actions in the "ovs-dpctl | |
1328 | dump-flows" output. | |
1329 | ||
1330 | 4. "tcpdump" the "eth" interface through which the ARP egresses | |
1331 | the physical machine. | |
1332 | ||
1333 | 5. "tcpdump" the "eth" interface through which the ARP | |
1334 | ingresses the physical machine, at the remote host that | |
1335 | receives the ARP. | |
1336 | ||
1337 | 6. Use "ovs-dpctl dump-flows" to spot the ARP flow on the | |
1338 | remote host that receives the ARP and observe the VM "vif" | |
1339 | or "tap" interface to which the flow is directed. Again, | |
1340 | "ovs-dpctl show" and "ovs-appctl ofproto/trace" might help. | |
1341 | ||
1342 | 7. "tcpdump" the "vif" or "tap" interface to which the ARP is | |
1343 | directed. | |
1344 | ||
1345 | 8. "tcpdump" the "eth" interface through which the ARP | |
1346 | ingresses a VM, from inside the VM. | |
1347 | ||
1348 | It is likely that during one of these steps you will figure out the | |
1349 | problem. If not, then follow the ARP reply back to the origin, in | |
1350 | reverse. | |
1351 | ||
0f5edef0 BP |
1352 | Q: How do I make a flow drop packets? |
1353 | ||
e5f1da19 BP |
1354 | A: To drop a packet is to receive it without forwarding it. OpenFlow |
1355 | explicitly specifies forwarding actions. Thus, a flow with an | |
1356 | empty set of actions does not forward packets anywhere, causing | |
1357 | them to be dropped. You can specify an empty set of actions with | |
1358 | "actions=" on the ovs-ofctl command line. For example: | |
0f5edef0 BP |
1359 | |
1360 | ovs-ofctl add-flow br0 priority=65535,actions= | |
1361 | ||
1362 | would cause every packet entering switch br0 to be dropped. | |
1363 | ||
1364 | You can write "drop" explicitly if you like. The effect is the | |
1365 | same. Thus, the following command also causes every packet | |
1366 | entering switch br0 to be dropped: | |
1367 | ||
1368 | ovs-ofctl add-flow br0 priority=65535,actions=drop | |
1369 | ||
e5f1da19 BP |
1370 | "drop" is not an action, either in OpenFlow or Open vSwitch. |
1371 | Rather, it is only a way to say that there are no actions. | |
1372 | ||
2fafc091 BP |
1373 | Q: I added a flow to send packets out the ingress port, like this: |
1374 | ||
1375 | ovs-ofctl add-flow br0 in_port=2,actions=2 | |
1376 | ||
1377 | but OVS drops the packets instead. | |
1378 | ||
1379 | A: Yes, OpenFlow requires a switch to ignore attempts to send a packet | |
1380 | out its ingress port. The rationale is that dropping these packets | |
1381 | makes it harder to loop the network. Sometimes this behavior can | |
1382 | even be convenient, e.g. it is often the desired behavior in a flow | |
1383 | that forwards a packet to several ports ("floods" the packet). | |
1384 | ||
1385 | Sometimes one really needs to send a packet out its ingress port. | |
1386 | In this case, output to OFPP_IN_PORT, which in ovs-ofctl syntax is | |
1387 | expressed as just "in_port", e.g.: | |
1388 | ||
1389 | ovs-ofctl add-flow br0 in_port=2,actions=in_port | |
1390 | ||
1391 | This also works in some circumstances where the flow doesn't match | |
1392 | on the input port. For example, if you know that your switch has | |
1393 | five ports numbered 2 through 6, then the following will send every | |
1394 | received packet out every port, even its ingress port: | |
1395 | ||
1396 | ovs-ofctl add-flow br0 actions=2,3,4,5,6,in_port | |
1397 | ||
1398 | or, equivalently: | |
1399 | ||
1400 | ovs-ofctl add-flow br0 actions=all,in_port | |
1401 | ||
1402 | Sometimes, in complicated flow tables with multiple levels of | |
1403 | "resubmit" actions, a flow needs to output to a particular port | |
1404 | that may or may not be the ingress port. It's difficult to take | |
1405 | advantage of OFPP_IN_PORT in this situation. To help, Open vSwitch | |
1406 | provides, as an OpenFlow extension, the ability to modify the | |
1407 | in_port field. Whatever value is currently in the in_port field is | |
1408 | the port to which outputs will be dropped, as well as the | |
1409 | destination for OFPP_IN_PORT. This means that the following will | |
1410 | reliably output to port 2 or to ports 2 through 6, respectively: | |
1411 | ||
1412 | ovs-ofctl add-flow br0 in_port=2,actions=load:0->NXM_OF_IN_PORT[],2 | |
1413 | ovs-ofctl add-flow br0 actions=load:0->NXM_OF_IN_PORT[],2,3,4,5,6 | |
1414 | ||
1415 | If the input port is important, then one may save and restore it on | |
1416 | the stack: | |
1417 | ||
1418 | ovs-ofctl add-flow br0 actions=push:NXM_OF_IN_PORT[],\ | |
1419 | load:0->NXM_OF_IN_PORT[],\ | |
1420 | 2,3,4,5,6,\ | |
1421 | pop:NXM_OF_IN_PORT[] | |
1422 | ||
d4ee72b4 BP |
1423 | Q: My bridge br0 has host 192.168.0.1 on port 1 and host 192.168.0.2 |
1424 | on port 2. I set up flows to forward only traffic destined to the | |
1425 | other host and drop other traffic, like this: | |
1426 | ||
1427 | priority=5,in_port=1,ip,nw_dst=192.168.0.2,actions=2 | |
1428 | priority=5,in_port=2,ip,nw_dst=192.168.0.1,actions=1 | |
1429 | priority=0,actions=drop | |
1430 | ||
1431 | But it doesn't work--I don't get any connectivity when I do this. | |
1432 | Why? | |
1433 | ||
1434 | A: These flows drop the ARP packets that IP hosts use to establish IP | |
1435 | connectivity over Ethernet. To solve the problem, add flows to | |
1436 | allow ARP to pass between the hosts: | |
1437 | ||
1438 | priority=5,in_port=1,arp,actions=2 | |
1439 | priority=5,in_port=2,arp,actions=1 | |
1440 | ||
1441 | This issue can manifest other ways, too. The following flows that | |
1442 | match on Ethernet addresses instead of IP addresses will also drop | |
1443 | ARP packets, because ARP requests are broadcast instead of being | |
1444 | directed to a specific host: | |
1445 | ||
1446 | priority=5,in_port=1,dl_dst=54:00:00:00:00:02,actions=2 | |
1447 | priority=5,in_port=2,dl_dst=54:00:00:00:00:01,actions=1 | |
1448 | priority=0,actions=drop | |
1449 | ||
1450 | The solution already described above will also work in this case. | |
1451 | It may be better to add flows to allow all multicast and broadcast | |
1452 | traffic: | |
1453 | ||
1454 | priority=5,in_port=1,dl_dst=01:00:00:00:00:00/01:00:00:00:00:00,actions=2 | |
1455 | priority=5,in_port=2,dl_dst=01:00:00:00:00:00/01:00:00:00:00:00,actions=1 | |
0f5edef0 | 1456 | |
c483d489 BP |
1457 | Contact |
1458 | ------- | |
1459 | ||
1460 | bugs@openvswitch.org | |
1461 | http://openvswitch.org/ |