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1 | Open vSwitch <http://openvswitch.org> |
2 | ||
3 | Frequently Asked Questions | |
4 | ========================== | |
5 | ||
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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 | |
30 | platform (kernel 2.6.18 and newer), including: KVM, VirtualBox, Xen, | |
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 | |
92 | includes tools (ovs-controller, ovs-ofctl, ovs-vsctl) that developers | |
93 | can script and extend to provide distributed vswitch capabilities | |
94 | that are closely integrated with their virtualization management | |
95 | platform. | |
96 | ||
97 | Q: Why doesn't Open vSwitch support distribution? | |
98 | ||
99 | A: Open vSwitch is intended to be a useful component for building | |
100 | flexible network infrastructure. There are many different approaches | |
101 | to distribution which balance trade-offs between simplicity, | |
102 | scalability, hardware compatibility, convergence times, logical | |
103 | forwarding model, etc. The goal of Open vSwitch is to be able to | |
104 | support all as a primitive building block rather than choose a | |
105 | particular point in the distributed design space. | |
106 | ||
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107 | Q: How can I contribute to the Open vSwitch Community? |
108 | ||
109 | A: You can start by joining the mailing lists and helping to answer | |
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110 | questions. You can also suggest improvements to documentation. If |
111 | you have a feature or bug you would like to work on, send a mail to | |
112 | one of the mailing lists: | |
113 | ||
114 | http://openvswitch.org/mlists/ | |
115 | ||
116 | ||
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117 | Releases |
118 | -------- | |
119 | ||
120 | Q: What does it mean for an Open vSwitch release to be LTS (long-term | |
121 | support)? | |
3fc7dc18 | 122 | |
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123 | A: All official releases have been through a comprehensive testing |
124 | process and are suitable for production use. Planned releases will | |
125 | occur several times a year. If a significant bug is identified in an | |
126 | LTS release, we will provide an updated release that includes the | |
127 | fix. Releases that are not LTS may not be fixed and may just be | |
128 | supplanted by the next major release. The current LTS release is | |
79a6e10e | 129 | 1.9.x. |
7b287e99 | 130 | |
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131 | Q: What Linux kernel versions does each Open vSwitch release work with? |
132 | ||
133 | A: The following table lists the Linux kernel versions against which the | |
134 | given versions of the Open vSwitch kernel module will successfully | |
135 | build. The Linux kernel versions are upstream kernel versions, so | |
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136 | Linux kernels modified from the upstream sources may not build in |
137 | some cases even if they are based on a supported version. This is | |
138 | most notably true of Red Hat Enterprise Linux (RHEL) kernels, which | |
139 | are extensively modified from upstream. | |
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140 | |
141 | Open vSwitch Linux kernel | |
142 | ------------ ------------- | |
143 | 1.4.x 2.6.18 to 3.2 | |
144 | 1.5.x 2.6.18 to 3.2 | |
145 | 1.6.x 2.6.18 to 3.2 | |
146 | 1.7.x 2.6.18 to 3.3 | |
147 | 1.8.x 2.6.18 to 3.4 | |
64807dfb | 148 | 1.9.x 2.6.18 to 3.8 |
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149 | 1.10.x 2.6.18 to 3.8 |
150 | 1.11.x 2.6.18 to 3.8 | |
7ceda296 | 151 | 1.12.x 2.6.18 to 3.9 |
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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. | |
157 | It should build against almost any kernel, certainly against 2.6.18 | |
158 | and later. | |
159 | ||
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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 | ||
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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 | |
171 | the possbility of incompatibilities. | |
172 | ||
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173 | Q: What features are not available in the Open vSwitch kernel datapath |
174 | that ships as part of the upstream Linux kernel? | |
175 | ||
176 | A: The kernel module in upstream Linux 3.3 and later does not include | |
0a740f48 | 177 | tunnel virtual ports, that is, interfaces with type "gre", |
a6ae068b | 178 | "ipsec_gre", "gre64", "ipsec_gre64", "vxlan", or "lisp". It is |
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179 | possible to create tunnels in Linux and attach them to Open vSwitch |
180 | as system devices. However, they cannot be dynamically created | |
181 | through the OVSDB protocol or set the tunnel ids as a flow action. | |
182 | ||
183 | Work is in progress in adding tunnel virtual ports to the upstream | |
184 | Linux version of the Open vSwitch kernel module. For now, if you | |
185 | need these features, use the kernel module from the Open vSwitch | |
186 | distribution instead of the upstream Linux kernel module. | |
187 | ||
188 | The upstream kernel module does not include patch ports, but this | |
189 | only matters for Open vSwitch 1.9 and earlier, because Open vSwitch | |
190 | 1.10 and later implement patch ports without using this kernel | |
191 | feature. | |
6302c641 | 192 | |
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193 | Q: What features are not available when using the userspace datapath? |
194 | ||
0a740f48 | 195 | A: Tunnel virtual ports are not supported, as described in the |
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196 | previous answer. It is also not possible to use queue-related |
197 | actions. On Linux kernels before 2.6.39, maximum-sized VLAN packets | |
198 | may not be transmitted. | |
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199 | |
200 | ||
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201 | Terminology |
202 | ----------- | |
203 | ||
204 | Q: I thought Open vSwitch was a virtual Ethernet switch, but the | |
205 | documentation keeps talking about bridges. What's a bridge? | |
206 | ||
207 | A: In networking, the terms "bridge" and "switch" are synonyms. Open | |
208 | vSwitch implements an Ethernet switch, which means that it is also | |
209 | an Ethernet bridge. | |
210 | ||
211 | Q: What's a VLAN? | |
212 | ||
213 | A: See the "VLAN" section below. | |
214 | ||
215 | ||
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216 | Basic Configuration |
217 | ------------------- | |
218 | ||
219 | Q: How do I configure a port as an access port? | |
220 | ||
221 | A: Add "tag=VLAN" to your "ovs-vsctl add-port" command. For example, | |
222 | the following commands configure br0 with eth0 as a trunk port (the | |
223 | default) and tap0 as an access port for VLAN 9: | |
224 | ||
225 | ovs-vsctl add-br br0 | |
226 | ovs-vsctl add-port br0 eth0 | |
227 | ovs-vsctl add-port br0 tap0 tag=9 | |
228 | ||
229 | If you want to configure an already added port as an access port, | |
230 | use "ovs-vsctl set", e.g.: | |
231 | ||
232 | ovs-vsctl set port tap0 tag=9 | |
233 | ||
234 | Q: How do I configure a port as a SPAN port, that is, enable mirroring | |
235 | of all traffic to that port? | |
236 | ||
237 | A: The following commands configure br0 with eth0 and tap0 as trunk | |
238 | ports. All traffic coming in or going out on eth0 or tap0 is also | |
239 | mirrored to tap1; any traffic arriving on tap1 is dropped: | |
240 | ||
241 | ovs-vsctl add-br br0 | |
242 | ovs-vsctl add-port br0 eth0 | |
243 | ovs-vsctl add-port br0 tap0 | |
244 | ovs-vsctl add-port br0 tap1 \ | |
245 | -- --id=@p get port tap1 \ | |
246 | -- --id=@m create mirror name=m0 select-all=true output-port=@p \ | |
247 | -- set bridge br0 mirrors=@m | |
248 | ||
249 | To later disable mirroring, run: | |
250 | ||
251 | ovs-vsctl clear bridge br0 mirrors | |
252 | ||
253 | Q: How do I configure a VLAN as an RSPAN VLAN, that is, enable | |
254 | mirroring of all traffic to that VLAN? | |
255 | ||
256 | A: The following commands configure br0 with eth0 as a trunk port and | |
257 | tap0 as an access port for VLAN 10. All traffic coming in or going | |
258 | out on tap0, as well as traffic coming in or going out on eth0 in | |
259 | VLAN 10, is also mirrored to VLAN 15 on eth0. The original tag for | |
260 | VLAN 10, in cases where one is present, is dropped as part of | |
261 | mirroring: | |
262 | ||
263 | ovs-vsctl add-br br0 | |
264 | ovs-vsctl add-port br0 eth0 | |
265 | ovs-vsctl add-port br0 tap0 tag=10 | |
266 | ovs-vsctl \ | |
267 | -- --id=@m create mirror name=m0 select-all=true select-vlan=10 \ | |
268 | output-vlan=15 \ | |
269 | -- set bridge br0 mirrors=@m | |
270 | ||
271 | To later disable mirroring, run: | |
272 | ||
273 | ovs-vsctl clear bridge br0 mirrors | |
274 | ||
275 | Mirroring to a VLAN can disrupt a network that contains unmanaged | |
276 | switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a | |
277 | GRE tunnel has fewer caveats than mirroring to a VLAN and should | |
278 | generally be preferred. | |
279 | ||
280 | Q: Can I mirror more than one input VLAN to an RSPAN VLAN? | |
281 | ||
282 | A: Yes, but mirroring to a VLAN strips the original VLAN tag in favor | |
283 | of the specified output-vlan. This loss of information may make | |
284 | the mirrored traffic too hard to interpret. | |
285 | ||
286 | To mirror multiple VLANs, use the commands above, but specify a | |
287 | comma-separated list of VLANs as the value for select-vlan. To | |
288 | mirror every VLAN, use the commands above, but omit select-vlan and | |
289 | its value entirely. | |
290 | ||
291 | When a packet arrives on a VLAN that is used as a mirror output | |
292 | VLAN, the mirror is disregarded. Instead, in standalone mode, OVS | |
293 | floods the packet across all the ports for which the mirror output | |
294 | VLAN is configured. (If an OpenFlow controller is in use, then it | |
295 | can override this behavior through the flow table.) If OVS is used | |
296 | as an intermediate switch, rather than an edge switch, this ensures | |
297 | that the RSPAN traffic is distributed through the network. | |
298 | ||
299 | Mirroring to a VLAN can disrupt a network that contains unmanaged | |
300 | switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a | |
301 | GRE tunnel has fewer caveats than mirroring to a VLAN and should | |
302 | generally be preferred. | |
303 | ||
304 | Q: How do I configure mirroring of all traffic to a GRE tunnel? | |
305 | ||
306 | A: The following commands configure br0 with eth0 and tap0 as trunk | |
307 | ports. All traffic coming in or going out on eth0 or tap0 is also | |
308 | mirrored to gre0, a GRE tunnel to the remote host 192.168.1.10; any | |
309 | traffic arriving on gre0 is dropped: | |
310 | ||
311 | ovs-vsctl add-br br0 | |
312 | ovs-vsctl add-port br0 eth0 | |
313 | ovs-vsctl add-port br0 tap0 | |
314 | ovs-vsctl add-port br0 gre0 \ | |
315 | -- set interface gre0 type=gre options:remote_ip=192.168.1.10 \ | |
316 | -- --id=@p get port gre0 \ | |
317 | -- --id=@m create mirror name=m0 select-all=true output-port=@p \ | |
318 | -- set bridge br0 mirrors=@m | |
319 | ||
320 | To later disable mirroring and destroy the GRE tunnel: | |
321 | ||
322 | ovs-vsctl clear bridge br0 mirrors | |
323 | ovs-vcstl del-port br0 gre0 | |
324 | ||
325 | Q: Does Open vSwitch support ERSPAN? | |
326 | ||
327 | A: No. ERSPAN is an undocumented proprietary protocol. As an | |
328 | alternative, Open vSwitch supports mirroring to a GRE tunnel (see | |
329 | above). | |
330 | ||
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331 | Q: How do I connect two bridges? |
332 | ||
333 | A: First, why do you want to do this? Two connected bridges are not | |
334 | much different from a single bridge, so you might as well just have | |
335 | a single bridge with all your ports on it. | |
336 | ||
337 | If you still want to connect two bridges, you can use a pair of | |
338 | patch ports. The following example creates bridges br0 and br1, | |
339 | adds eth0 and tap0 to br0, adds tap1 to br1, and then connects br0 | |
340 | and br1 with a pair of patch ports. | |
341 | ||
342 | ovs-vsctl add-br br0 | |
343 | ovs-vsctl add-port br0 eth0 | |
344 | ovs-vsctl add-port br0 tap0 | |
345 | ovs-vsctl add-br br1 | |
346 | ovs-vsctl add-port br1 tap1 | |
347 | ovs-vsctl \ | |
348 | -- add-port br0 patch0 \ | |
349 | -- set interface patch0 type=patch options:peer=patch1 \ | |
350 | -- add-port br1 patch1 \ | |
351 | -- set interface patch1 type=patch options:peer=patch0 | |
352 | ||
353 | Bridges connected with patch ports are much like a single bridge. | |
354 | For instance, if the example above also added eth1 to br1, and both | |
355 | eth0 and eth1 happened to be connected to the same next-hop switch, | |
356 | then you could loop your network just as you would if you added | |
357 | eth0 and eth1 to the same bridge (see the "Configuration Problems" | |
358 | section below for more information). | |
359 | ||
360 | If you are using Open vSwitch 1.9 or an earlier version, then you | |
361 | need to be using the kernel module bundled with Open vSwitch rather | |
362 | than the one that is integrated into Linux 3.3 and later, because | |
363 | Open vSwitch 1.9 and earlier versions need kernel support for patch | |
364 | ports. This also means that in Open vSwitch 1.9 and earlier, patch | |
365 | ports will not work with the userspace datapath, only with the | |
366 | kernel module. | |
367 | ||
a70fc0cf JP |
368 | Q: Why are there so many different ways to dump flows? |
369 | ||
370 | A: Open vSwitch uses different kinds of flows for different purposes: | |
371 | ||
372 | - OpenFlow flows are the most important kind of flow. OpenFlow | |
373 | controllers use these flows to define a switch's policy. | |
374 | OpenFlow flows support wildcards, priorities, and multiple | |
375 | tables. | |
376 | ||
377 | When in-band control is in use, Open vSwitch sets up a few | |
378 | "hidden" flows, with priority higher than a controller or the | |
379 | user can configure, that are not visible via OpenFlow. (See | |
380 | the "Controller" section of the FAQ for more information | |
381 | about hidden flows.) | |
382 | ||
383 | - The Open vSwitch software switch implementation uses a second | |
384 | kind of flow internally. These flows, called "exact-match" | |
385 | or "datapath" or "kernel" flows, do not support wildcards or | |
386 | priorities and comprise only a single table, which makes them | |
387 | suitable for caching. OpenFlow flows and exact-match flows | |
388 | also support different actions and number ports differently. | |
389 | ||
390 | Exact-match flows are an implementation detail that is | |
391 | subject to change in future versions of Open vSwitch. Even | |
392 | with the current version of Open vSwitch, hardware switch | |
393 | implementations do not necessarily use exact-match flows. | |
394 | ||
395 | Each of the commands for dumping flows has a different purpose: | |
396 | ||
397 | - "ovs-ofctl dump-flows <br>" dumps OpenFlow flows, excluding | |
398 | hidden flows. This is the most commonly useful form of flow | |
399 | dump. (Unlike the other commands, this should work with any | |
400 | OpenFlow switch, not just Open vSwitch.) | |
401 | ||
402 | - "ovs-appctl bridge/dump-flows <br>" dumps OpenFlow flows, | |
403 | including hidden flows. This is occasionally useful for | |
404 | troubleshooting suspected issues with in-band control. | |
405 | ||
406 | - "ovs-dpctl dump-flows [dp]" dumps the exact-match flow table | |
407 | entries for a Linux kernel-based datapath. In Open vSwitch | |
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408 | 1.10 and later, ovs-vswitchd merges multiple switches into a |
409 | single datapath, so it will show all the flows on all your | |
410 | kernel-based switches. This command can occasionally be | |
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411 | useful for debugging. |
412 | ||
413 | - "ovs-appctl dpif/dump-flows <br>", new in Open vSwitch 1.10, | |
414 | dumps exact-match flows for only the specified bridge, | |
415 | regardless of the type. | |
416 | ||
717e7c8d | 417 | |
c483d489 BP |
418 | Configuration Problems |
419 | ---------------------- | |
420 | ||
421 | Q: I created a bridge and added my Ethernet port to it, using commands | |
422 | like these: | |
423 | ||
424 | ovs-vsctl add-br br0 | |
425 | ovs-vsctl add-port br0 eth0 | |
426 | ||
427 | and as soon as I ran the "add-port" command I lost all connectivity | |
428 | through eth0. Help! | |
429 | ||
430 | A: A physical Ethernet device that is part of an Open vSwitch bridge | |
431 | should not have an IP address. If one does, then that IP address | |
432 | will not be fully functional. | |
433 | ||
434 | You can restore functionality by moving the IP address to an Open | |
435 | vSwitch "internal" device, such as the network device named after | |
436 | the bridge itself. For example, assuming that eth0's IP address is | |
437 | 192.168.128.5, you could run the commands below to fix up the | |
438 | situation: | |
439 | ||
440 | ifconfig eth0 0.0.0.0 | |
441 | ifconfig br0 192.168.128.5 | |
442 | ||
443 | (If your only connection to the machine running OVS is through the | |
444 | IP address in question, then you would want to run all of these | |
445 | commands on a single command line, or put them into a script.) If | |
446 | there were any additional routes assigned to eth0, then you would | |
447 | also want to use commands to adjust these routes to go through br0. | |
448 | ||
449 | If you use DHCP to obtain an IP address, then you should kill the | |
450 | DHCP client that was listening on the physical Ethernet interface | |
451 | (e.g. eth0) and start one listening on the internal interface | |
452 | (e.g. br0). You might still need to manually clear the IP address | |
453 | from the physical interface (e.g. with "ifconfig eth0 0.0.0.0"). | |
454 | ||
455 | There is no compelling reason why Open vSwitch must work this way. | |
456 | However, this is the way that the Linux kernel bridge module has | |
457 | always worked, so it's a model that those accustomed to Linux | |
458 | bridging are already used to. Also, the model that most people | |
459 | expect is not implementable without kernel changes on all the | |
460 | versions of Linux that Open vSwitch supports. | |
461 | ||
462 | By the way, this issue is not specific to physical Ethernet | |
463 | devices. It applies to all network devices except Open vswitch | |
464 | "internal" devices. | |
465 | ||
466 | Q: I created a bridge and added a couple of Ethernet ports to it, | |
467 | using commands like these: | |
468 | ||
469 | ovs-vsctl add-br br0 | |
470 | ovs-vsctl add-port br0 eth0 | |
471 | ovs-vsctl add-port br0 eth1 | |
472 | ||
473 | and now my network seems to have melted: connectivity is unreliable | |
474 | (even connectivity that doesn't go through Open vSwitch), all the | |
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475 | LEDs on my physical switches are blinking, wireshark shows |
476 | duplicated packets, and CPU usage is very high. | |
c483d489 BP |
477 | |
478 | A: More than likely, you've looped your network. Probably, eth0 and | |
479 | eth1 are connected to the same physical Ethernet switch. This | |
480 | yields a scenario where OVS receives a broadcast packet on eth0 and | |
481 | sends it out on eth1, then the physical switch connected to eth1 | |
482 | sends the packet back on eth0, and so on forever. More complicated | |
483 | scenarios, involving a loop through multiple switches, are possible | |
484 | too. | |
485 | ||
486 | The solution depends on what you are trying to do: | |
487 | ||
488 | - If you added eth0 and eth1 to get higher bandwidth or higher | |
489 | reliability between OVS and your physical Ethernet switch, | |
490 | use a bond. The following commands create br0 and then add | |
491 | eth0 and eth1 as a bond: | |
492 | ||
493 | ovs-vsctl add-br br0 | |
494 | ovs-vsctl add-bond br0 bond0 eth0 eth1 | |
495 | ||
496 | Bonds have tons of configuration options. Please read the | |
497 | documentation on the Port table in ovs-vswitchd.conf.db(5) | |
498 | for all the details. | |
499 | ||
500 | - Perhaps you don't actually need eth0 and eth1 to be on the | |
501 | same bridge. For example, if you simply want to be able to | |
502 | connect each of them to virtual machines, then you can put | |
503 | each of them on a bridge of its own: | |
504 | ||
505 | ovs-vsctl add-br br0 | |
506 | ovs-vsctl add-port br0 eth0 | |
507 | ||
508 | ovs-vsctl add-br br1 | |
509 | ovs-vsctl add-port br1 eth1 | |
510 | ||
511 | and then connect VMs to br0 and br1. (A potential | |
512 | disadvantage is that traffic cannot directly pass between br0 | |
513 | and br1. Instead, it will go out eth0 and come back in eth1, | |
514 | or vice versa.) | |
515 | ||
516 | - If you have a redundant or complex network topology and you | |
517 | want to prevent loops, turn on spanning tree protocol (STP). | |
518 | The following commands create br0, enable STP, and add eth0 | |
519 | and eth1 to the bridge. The order is important because you | |
520 | don't want have to have a loop in your network even | |
521 | transiently: | |
522 | ||
523 | ovs-vsctl add-br br0 | |
524 | ovs-vsctl set bridge br0 stp_enable=true | |
525 | ovs-vsctl add-port br0 eth0 | |
526 | ovs-vsctl add-port br0 eth1 | |
527 | ||
528 | The Open vSwitch implementation of STP is not well tested. | |
529 | Please report any bugs you observe, but if you'd rather avoid | |
530 | acting as a beta tester then another option might be your | |
531 | best shot. | |
532 | ||
533 | Q: I can't seem to use Open vSwitch in a wireless network. | |
534 | ||
535 | A: Wireless base stations generally only allow packets with the source | |
536 | MAC address of NIC that completed the initial handshake. | |
537 | Therefore, without MAC rewriting, only a single device can | |
538 | communicate over a single wireless link. | |
539 | ||
540 | This isn't specific to Open vSwitch, it's enforced by the access | |
541 | point, so the same problems will show up with the Linux bridge or | |
542 | any other way to do bridging. | |
543 | ||
8748ec7b BP |
544 | Q: I can't seem to add my PPP interface to an Open vSwitch bridge. |
545 | ||
546 | A: PPP most commonly carries IP packets, but Open vSwitch works only | |
547 | with Ethernet frames. The correct way to interface PPP to an | |
548 | Ethernet network is usually to use routing instead of switching. | |
549 | ||
5aa75474 BP |
550 | Q: Is there any documentation on the database tables and fields? |
551 | ||
552 | A: Yes. ovs-vswitchd.conf.db(5) is a comprehensive reference. | |
553 | ||
acf60855 JP |
554 | Q: When I run ovs-dpctl I no longer see the bridges I created. Instead, |
555 | I only see a datapath called "ovs-system". How can I see datapath | |
556 | information about a particular bridge? | |
557 | ||
558 | A: In version 1.9.0, OVS switched to using a single datapath that is | |
559 | shared by all bridges of that type. The "ovs-appctl dpif/*" | |
560 | commands provide similar functionality that is scoped by the bridge. | |
561 | ||
c483d489 | 562 | |
bceafb63 BP |
563 | Quality of Service (QoS) |
564 | ------------------------ | |
565 | ||
566 | Q: How do I configure Quality of Service (QoS)? | |
567 | ||
568 | A: Suppose that you want to set up bridge br0 connected to physical | |
569 | Ethernet port eth0 (a 1 Gbps device) and virtual machine interfaces | |
570 | vif1.0 and vif2.0, and that you want to limit traffic from vif1.0 | |
571 | to eth0 to 10 Mbps and from vif2.0 to eth0 to 20 Mbps. Then, you | |
572 | could configure the bridge this way: | |
573 | ||
574 | ovs-vsctl -- \ | |
575 | add-br br0 -- \ | |
576 | add-port br0 eth0 -- \ | |
577 | add-port br0 vif1.0 -- set interface vif1.0 ofport_request=5 -- \ | |
578 | add-port br0 vif2.0 -- set interface vif2.0 ofport_request=6 -- \ | |
579 | set port eth0 qos=@newqos -- \ | |
580 | --id=@newqos create qos type=linux-htb \ | |
581 | other-config:max-rate=1000000000 \ | |
582 | queues:123=@vif10queue \ | |
583 | queues:234=@vif20queue -- \ | |
584 | --id=@vif10queue create queue other-config:max-rate=10000000 -- \ | |
585 | --id=@vif20queue create queue other-config:max-rate=20000000 | |
586 | ||
587 | At this point, bridge br0 is configured with the ports and eth0 is | |
588 | configured with the queues that you need for QoS, but nothing is | |
589 | actually directing packets from vif1.0 or vif2.0 to the queues that | |
590 | we have set up for them. That means that all of the packets to | |
591 | eth0 are going to the "default queue", which is not what we want. | |
592 | ||
593 | We use OpenFlow to direct packets from vif1.0 and vif2.0 to the | |
594 | queues reserved for them: | |
595 | ||
596 | ovs-ofctl add-flow br0 in_port=5,actions=set_queue:123,normal | |
597 | ovs-ofctl add-flow br0 in_port=6,actions=set_queue:234,normal | |
598 | ||
599 | Each of the above flows matches on the input port, sets up the | |
600 | appropriate queue (123 for vif1.0, 234 for vif2.0), and then | |
601 | executes the "normal" action, which performs the same switching | |
602 | that Open vSwitch would have done without any OpenFlow flows being | |
603 | present. (We know that vif1.0 and vif2.0 have OpenFlow port | |
604 | numbers 5 and 6, respectively, because we set their ofport_request | |
605 | columns above. If we had not done that, then we would have needed | |
606 | to find out their port numbers before setting up these flows.) | |
607 | ||
608 | Now traffic going from vif1.0 or vif2.0 to eth0 should be | |
609 | rate-limited. | |
610 | ||
611 | By the way, if you delete the bridge created by the above commands, | |
612 | with: | |
613 | ||
614 | ovs-vsctl del-br br0 | |
615 | ||
616 | then that will leave one unreferenced QoS record and two | |
617 | unreferenced Queue records in the Open vSwich database. One way to | |
618 | clear them out, assuming you don't have other QoS or Queue records | |
619 | that you want to keep, is: | |
620 | ||
621 | ovs-vsctl -- --all destroy QoS -- --all destroy Queue | |
622 | ||
7839bb41 BP |
623 | If you do want to keep some QoS or Queue records, or the Open |
624 | vSwitch you are using is older than version 1.8 (which added the | |
625 | --all option), then you will have to destroy QoS and Queue records | |
626 | individually. | |
627 | ||
bceafb63 BP |
628 | Q: I configured Quality of Service (QoS) in my OpenFlow network by |
629 | adding records to the QoS and Queue table, but the results aren't | |
630 | what I expect. | |
631 | ||
632 | A: Did you install OpenFlow flows that use your queues? This is the | |
633 | primary way to tell Open vSwitch which queues you want to use. If | |
634 | you don't do this, then the default queue will be used, which will | |
635 | probably not have the effect you want. | |
636 | ||
637 | Refer to the previous question for an example. | |
638 | ||
639 | Q: I configured QoS, correctly, but my measurements show that it isn't | |
640 | working as well as I expect. | |
641 | ||
642 | A: With the Linux kernel, the Open vSwitch implementation of QoS has | |
643 | two aspects: | |
644 | ||
645 | - Open vSwitch configures a subset of Linux kernel QoS | |
646 | features, according to what is in OVSDB. It is possible that | |
647 | this code has bugs. If you believe that this is so, then you | |
648 | can configure the Linux traffic control (QoS) stack directly | |
649 | with the "tc" program. If you get better results that way, | |
650 | you can send a detailed bug report to bugs@openvswitch.org. | |
651 | ||
652 | It is certain that Open vSwitch cannot configure every Linux | |
653 | kernel QoS feature. If you need some feature that OVS cannot | |
654 | configure, then you can also use "tc" directly (or add that | |
655 | feature to OVS). | |
656 | ||
657 | - The Open vSwitch implementation of OpenFlow allows flows to | |
658 | be directed to particular queues. This is pretty simple and | |
659 | unlikely to have serious bugs at this point. | |
660 | ||
661 | However, most problems with QoS on Linux are not bugs in Open | |
662 | vSwitch at all. They tend to be either configuration errors | |
663 | (please see the earlier questions in this section) or issues with | |
664 | the traffic control (QoS) stack in Linux. The Open vSwitch | |
665 | developers are not experts on Linux traffic control. We suggest | |
666 | that, if you believe you are encountering a problem with Linux | |
667 | traffic control, that you consult the tc manpages (e.g. tc(8), | |
668 | tc-htb(8), tc-hfsc(8)), web resources (e.g. http://lartc.org/), or | |
669 | mailing lists (e.g. http://vger.kernel.org/vger-lists.html#netdev). | |
670 | ||
671 | ||
c483d489 BP |
672 | VLANs |
673 | ----- | |
674 | ||
14481051 BP |
675 | Q: What's a VLAN? |
676 | ||
677 | A: At the simplest level, a VLAN (short for "virtual LAN") is a way to | |
678 | partition a single switch into multiple switches. Suppose, for | |
679 | example, that you have two groups of machines, group A and group B. | |
680 | You want the machines in group A to be able to talk to each other, | |
681 | and you want the machine in group B to be able to talk to each | |
682 | other, but you don't want the machines in group A to be able to | |
683 | talk to the machines in group B. You can do this with two | |
684 | switches, by plugging the machines in group A into one switch and | |
685 | the machines in group B into the other switch. | |
686 | ||
687 | If you only have one switch, then you can use VLANs to do the same | |
688 | thing, by configuring the ports for machines in group A as VLAN | |
689 | "access ports" for one VLAN and the ports for group B as "access | |
690 | ports" for a different VLAN. The switch will only forward packets | |
691 | between ports that are assigned to the same VLAN, so this | |
692 | effectively subdivides your single switch into two independent | |
693 | switches, one for each group of machines. | |
694 | ||
695 | So far we haven't said anything about VLAN headers. With access | |
696 | ports, like we've described so far, no VLAN header is present in | |
697 | the Ethernet frame. This means that the machines (or switches) | |
698 | connected to access ports need not be aware that VLANs are | |
699 | involved, just like in the case where we use two different physical | |
700 | switches. | |
701 | ||
702 | Now suppose that you have a whole bunch of switches in your | |
703 | network, instead of just one, and that some machines in group A are | |
704 | connected directly to both switches 1 and 2. To allow these | |
705 | machines to talk to each other, you could add an access port for | |
706 | group A's VLAN to switch 1 and another to switch 2, and then | |
707 | connect an Ethernet cable between those ports. That works fine, | |
708 | but it doesn't scale well as the number of switches and the number | |
709 | of VLANs increases, because you use up a lot of valuable switch | |
710 | ports just connecting together your VLANs. | |
711 | ||
712 | This is where VLAN headers come in. Instead of using one cable and | |
713 | two ports per VLAN to connect a pair of switches, we configure a | |
714 | port on each switch as a VLAN "trunk port". Packets sent and | |
715 | received on a trunk port carry a VLAN header that says what VLAN | |
716 | the packet belongs to, so that only two ports total are required to | |
717 | connect the switches, regardless of the number of VLANs in use. | |
718 | Normally, only switches (either physical or virtual) are connected | |
719 | to a trunk port, not individual hosts, because individual hosts | |
720 | don't expect to see a VLAN header in the traffic that they receive. | |
721 | ||
722 | None of the above discussion says anything about particular VLAN | |
723 | numbers. This is because VLAN numbers are completely arbitrary. | |
724 | One must only ensure that a given VLAN is numbered consistently | |
725 | throughout a network and that different VLANs are given different | |
726 | numbers. (That said, VLAN 0 is usually synonymous with a packet | |
727 | that has no VLAN header, and VLAN 4095 is reserved.) | |
728 | ||
c483d489 BP |
729 | Q: VLANs don't work. |
730 | ||
731 | A: Many drivers in Linux kernels before version 3.3 had VLAN-related | |
732 | bugs. If you are having problems with VLANs that you suspect to be | |
733 | driver related, then you have several options: | |
734 | ||
735 | - Upgrade to Linux 3.3 or later. | |
736 | ||
737 | - Build and install a fixed version of the particular driver | |
738 | that is causing trouble, if one is available. | |
739 | ||
740 | - Use a NIC whose driver does not have VLAN problems. | |
741 | ||
742 | - Use "VLAN splinters", a feature in Open vSwitch 1.4 and later | |
743 | that works around bugs in kernel drivers. To enable VLAN | |
744 | splinters on interface eth0, use the command: | |
745 | ||
7b287e99 | 746 | ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true |
c483d489 BP |
747 | |
748 | For VLAN splinters to be effective, Open vSwitch must know | |
749 | which VLANs are in use. See the "VLAN splinters" section in | |
750 | the Interface table in ovs-vswitchd.conf.db(5) for details on | |
751 | how Open vSwitch infers in-use VLANs. | |
752 | ||
753 | VLAN splinters increase memory use and reduce performance, so | |
754 | use them only if needed. | |
755 | ||
756 | - Apply the "vlan workaround" patch from the XenServer kernel | |
757 | patch queue, build Open vSwitch against this patched kernel, | |
758 | and then use ovs-vlan-bug-workaround(8) to enable the VLAN | |
759 | workaround for each interface whose driver is buggy. | |
760 | ||
761 | (This is a nontrivial exercise, so this option is included | |
762 | only for completeness.) | |
763 | ||
764 | It is not always easy to tell whether a Linux kernel driver has | |
765 | buggy VLAN support. The ovs-vlan-test(8) and ovs-test(8) utilities | |
766 | can help you test. See their manpages for details. Of the two | |
767 | utilities, ovs-test(8) is newer and more thorough, but | |
768 | ovs-vlan-test(8) may be easier to use. | |
769 | ||
770 | Q: VLANs still don't work. I've tested the driver so I know that it's OK. | |
771 | ||
772 | A: Do you have VLANs enabled on the physical switch that OVS is | |
773 | attached to? Make sure that the port is configured to trunk the | |
774 | VLAN or VLANs that you are using with OVS. | |
775 | ||
776 | Q: Outgoing VLAN-tagged traffic goes through OVS to my physical switch | |
777 | and to its destination host, but OVS seems to drop incoming return | |
778 | traffic. | |
779 | ||
780 | A: It's possible that you have the VLAN configured on your physical | |
781 | switch as the "native" VLAN. In this mode, the switch treats | |
782 | incoming packets either tagged with the native VLAN or untagged as | |
783 | part of the native VLAN. It may also send outgoing packets in the | |
784 | native VLAN without a VLAN tag. | |
785 | ||
786 | If this is the case, you have two choices: | |
787 | ||
788 | - Change the physical switch port configuration to tag packets | |
789 | it forwards to OVS with the native VLAN instead of forwarding | |
790 | them untagged. | |
791 | ||
792 | - Change the OVS configuration for the physical port to a | |
793 | native VLAN mode. For example, the following sets up a | |
794 | bridge with port eth0 in "native-tagged" mode in VLAN 9: | |
795 | ||
796 | ovs-vsctl add-br br0 | |
797 | ovs-vsctl add-port br0 eth0 tag=9 vlan_mode=native-tagged | |
798 | ||
799 | In this situation, "native-untagged" mode will probably work | |
800 | equally well. Refer to the documentation for the Port table | |
801 | in ovs-vswitchd.conf.db(5) for more information. | |
802 | ||
8d45e938 BP |
803 | Q: I added a pair of VMs on different VLANs, like this: |
804 | ||
805 | ovs-vsctl add-br br0 | |
806 | ovs-vsctl add-port br0 eth0 | |
807 | ovs-vsctl add-port br0 tap0 tag=9 | |
808 | ovs-vsctl add-port br0 tap1 tag=10 | |
809 | ||
810 | but the VMs can't access each other, the external network, or the | |
811 | Internet. | |
812 | ||
813 | A: It is to be expected that the VMs can't access each other. VLANs | |
814 | are a means to partition a network. When you configured tap0 and | |
815 | tap1 as access ports for different VLANs, you indicated that they | |
816 | should be isolated from each other. | |
817 | ||
818 | As for the external network and the Internet, it seems likely that | |
819 | the machines you are trying to access are not on VLAN 9 (or 10) and | |
820 | that the Internet is not available on VLAN 9 (or 10). | |
821 | ||
3c8399a2 BP |
822 | Q: I added a pair of VMs on the same VLAN, like this: |
823 | ||
824 | ovs-vsctl add-br br0 | |
825 | ovs-vsctl add-port br0 eth0 | |
826 | ovs-vsctl add-port br0 tap0 tag=9 | |
827 | ovs-vsctl add-port br0 tap1 tag=9 | |
828 | ||
829 | The VMs can access each other, but not the external network or the | |
830 | Internet. | |
831 | ||
832 | A: It seems likely that the machines you are trying to access in the | |
833 | external network are not on VLAN 9 and that the Internet is not | |
834 | available on VLAN 9. Also, ensure VLAN 9 is set up as an allowed | |
835 | trunk VLAN on the upstream switch port to which eth0 is connected. | |
836 | ||
c483d489 BP |
837 | Q: Can I configure an IP address on a VLAN? |
838 | ||
839 | A: Yes. Use an "internal port" configured as an access port. For | |
840 | example, the following configures IP address 192.168.0.7 on VLAN 9. | |
841 | That is, OVS will forward packets from eth0 to 192.168.0.7 only if | |
842 | they have an 802.1Q header with VLAN 9. Conversely, traffic | |
843 | forwarded from 192.168.0.7 to eth0 will be tagged with an 802.1Q | |
844 | header with VLAN 9: | |
845 | ||
846 | ovs-vsctl add-br br0 | |
847 | ovs-vsctl add-port br0 eth0 | |
848 | ovs-vsctl add-port br0 vlan9 tag=9 -- set interface vlan9 type=internal | |
849 | ifconfig vlan9 192.168.0.7 | |
850 | ||
851 | Q: My OpenFlow controller doesn't see the VLANs that I expect. | |
852 | ||
853 | A: The configuration for VLANs in the Open vSwitch database (e.g. via | |
854 | ovs-vsctl) only affects traffic that goes through Open vSwitch's | |
855 | implementation of the OpenFlow "normal switching" action. By | |
856 | default, when Open vSwitch isn't connected to a controller and | |
857 | nothing has been manually configured in the flow table, all traffic | |
858 | goes through the "normal switching" action. But, if you set up | |
859 | OpenFlow flows on your own, through a controller or using ovs-ofctl | |
860 | or through other means, then you have to implement VLAN handling | |
861 | yourself. | |
862 | ||
863 | You can use "normal switching" as a component of your OpenFlow | |
864 | actions, e.g. by putting "normal" into the lists of actions on | |
865 | ovs-ofctl or by outputting to OFPP_NORMAL from an OpenFlow | |
241241f5 BP |
866 | controller. In situations where this is not suitable, you can |
867 | implement VLAN handling yourself, e.g.: | |
868 | ||
869 | - If a packet comes in on an access port, and the flow table | |
870 | needs to send it out on a trunk port, then the flow can add | |
871 | the appropriate VLAN tag with the "mod_vlan_vid" action. | |
872 | ||
873 | - If a packet comes in on a trunk port, and the flow table | |
874 | needs to send it out on an access port, then the flow can | |
875 | strip the VLAN tag with the "strip_vlan" action. | |
c483d489 | 876 | |
f0a0c1a6 BP |
877 | Q: I configured ports on a bridge as access ports with different VLAN |
878 | tags, like this: | |
879 | ||
880 | ovs-vsctl add-br br0 | |
881 | ovs-vsctl set-controller br0 tcp:192.168.0.10:6633 | |
882 | ovs-vsctl add-port br0 eth0 | |
883 | ovs-vsctl add-port br0 tap0 tag=9 | |
884 | ovs-vsctl add-port br0 tap1 tag=10 | |
885 | ||
886 | but the VMs running behind tap0 and tap1 can still communicate, | |
887 | that is, they are not isolated from each other even though they are | |
888 | on different VLANs. | |
889 | ||
890 | A: Do you have a controller configured on br0 (as the commands above | |
891 | do)? If so, then this is a variant on the previous question, "My | |
892 | OpenFlow controller doesn't see the VLANs that I expect," and you | |
893 | can refer to the answer there for more information. | |
894 | ||
c483d489 | 895 | |
0edbe3fb KM |
896 | VXLANs |
897 | ----- | |
898 | ||
899 | Q: What's a VXLAN? | |
900 | ||
901 | A: VXLAN stands for Virtual eXtensible Local Area Network, and is a means | |
902 | to solve the scaling challenges of VLAN networks in a multi-tenant | |
903 | environment. VXLAN is an overlay network which transports an L2 network | |
904 | over an existing L3 network. For more information on VXLAN, please see | |
905 | the IETF draft available here: | |
906 | ||
907 | http://tools.ietf.org/html/draft-mahalingam-dutt-dcops-vxlan-03 | |
908 | ||
909 | Q: How much of the VXLAN protocol does Open vSwitch currently support? | |
910 | ||
911 | A: Open vSwitch currently supports the framing format for packets on the | |
912 | wire. There is currently no support for the multicast aspects of VXLAN. | |
913 | To get around the lack of multicast support, it is possible to | |
914 | pre-provision MAC to IP address mappings either manually or from a | |
915 | controller. | |
916 | ||
917 | Q: What destination UDP port does the VXLAN implementation in Open vSwitch | |
918 | use? | |
919 | ||
920 | A: By default, Open vSwitch will use the assigned IANA port for VXLAN, which | |
921 | is 4789. However, it is possible to configure the destination UDP port | |
922 | manually on a per-VXLAN tunnel basis. An example of this configuration is | |
923 | provided below. | |
924 | ||
925 | ovs-vsctl add-br br0 | |
926 | ovs-vsctl add-port br0 vxlan1 -- set interface vxlan1 | |
927 | type=vxlan options:remote_ip=192.168.1.2 options:key=flow | |
928 | options:dst_port=8472 | |
929 | ||
930 | ||
0f5edef0 BP |
931 | Using OpenFlow (Manually or Via Controller) |
932 | ------------------------------------------- | |
c483d489 | 933 | |
7b287e99 JP |
934 | Q: What versions of OpenFlow does Open vSwitch support? |
935 | ||
8e70e196 BP |
936 | A: Open vSwitch 1.9 and earlier support only OpenFlow 1.0 (plus |
937 | extensions that bring in many of the features from later versions | |
938 | of OpenFlow). | |
7b287e99 | 939 | |
75fa58f8 BP |
940 | Open vSwitch 1.10 and later have experimental support for OpenFlow |
941 | 1.2 and 1.3. On these versions of Open vSwitch, the following | |
942 | command enables OpenFlow 1.0, 1.2, and 1.3 on bridge br0: | |
8e70e196 | 943 | |
12eadc32 | 944 | ovs-vsctl set bridge br0 protocols=OpenFlow10,OpenFlow12,OpenFlow13 |
8e70e196 | 945 | |
75fa58f8 BP |
946 | Open vSwitch version 1.12 and later will have experimental support |
947 | for OpenFlow 1.1, 1.2, and 1.3. On these versions of Open vSwitch, | |
948 | the following command enables OpenFlow 1.0, 1.1, 1.2, and 1.3 on | |
949 | bridge br0: | |
950 | ||
951 | ovs-vsctl set bridge br0 protocols=OpenFlow10,OpenFlow11,OpenFlow12,OpenFlow13 | |
952 | ||
ac12b4cb BP |
953 | Use the -O option to enable support for later versions of OpenFlow |
954 | in ovs-ofctl. For example: | |
955 | ||
956 | ovs-ofctl -O OpenFlow13 dump-flows br0 | |
957 | ||
75fa58f8 BP |
958 | Support for OpenFlow 1.1, 1.2, and 1.3 is still incomplete. Work |
959 | to be done is tracked in OPENFLOW-1.1+ in the Open vSwitch sources | |
8e70e196 BP |
960 | (also via http://openvswitch.org/development/openflow-1-x-plan/). |
961 | When support for a given OpenFlow version is solidly implemented, | |
962 | Open vSwitch will enable that version by default. | |
7b287e99 | 963 | |
c483d489 BP |
964 | Q: I'm getting "error type 45250 code 0". What's that? |
965 | ||
966 | A: This is a Open vSwitch extension to OpenFlow error codes. Open | |
967 | vSwitch uses this extension when it must report an error to an | |
968 | OpenFlow controller but no standard OpenFlow error code is | |
969 | suitable. | |
970 | ||
971 | Open vSwitch logs the errors that it sends to controllers, so the | |
972 | easiest thing to do is probably to look at the ovs-vswitchd log to | |
973 | find out what the error was. | |
974 | ||
975 | If you want to dissect the extended error message yourself, the | |
976 | format is documented in include/openflow/nicira-ext.h in the Open | |
977 | vSwitch source distribution. The extended error codes are | |
978 | documented in lib/ofp-errors.h. | |
979 | ||
980 | Q1: Some of the traffic that I'd expect my OpenFlow controller to see | |
981 | doesn't actually appear through the OpenFlow connection, even | |
982 | though I know that it's going through. | |
983 | Q2: Some of the OpenFlow flows that my controller sets up don't seem | |
984 | to apply to certain traffic, especially traffic between OVS and | |
985 | the controller itself. | |
986 | ||
987 | A: By default, Open vSwitch assumes that OpenFlow controllers are | |
988 | connected "in-band", that is, that the controllers are actually | |
989 | part of the network that is being controlled. In in-band mode, | |
990 | Open vSwitch sets up special "hidden" flows to make sure that | |
991 | traffic can make it back and forth between OVS and the controllers. | |
992 | These hidden flows are higher priority than any flows that can be | |
993 | set up through OpenFlow, and they are not visible through normal | |
994 | OpenFlow flow table dumps. | |
995 | ||
996 | Usually, the hidden flows are desirable and helpful, but | |
997 | occasionally they can cause unexpected behavior. You can view the | |
998 | full OpenFlow flow table, including hidden flows, on bridge br0 | |
999 | with the command: | |
1000 | ||
1001 | ovs-appctl bridge/dump-flows br0 | |
1002 | ||
1003 | to help you debug. The hidden flows are those with priorities | |
1004 | greater than 65535 (the maximum priority that can be set with | |
1005 | OpenFlow). | |
1006 | ||
1007 | The DESIGN file at the top level of the Open vSwitch source | |
1008 | distribution describes the in-band model in detail. | |
1009 | ||
1010 | If your controllers are not actually in-band (e.g. they are on | |
1011 | localhost via 127.0.0.1, or on a separate network), then you should | |
1012 | configure your controllers in "out-of-band" mode. If you have one | |
1013 | controller on bridge br0, then you can configure out-of-band mode | |
1014 | on it with: | |
1015 | ||
1016 | ovs-vsctl set controller br0 connection-mode=out-of-band | |
1017 | ||
1018 | Q: I configured all my controllers for out-of-band control mode but | |
1019 | "ovs-appctl bridge/dump-flows" still shows some hidden flows. | |
1020 | ||
1021 | A: You probably have a remote manager configured (e.g. with "ovs-vsctl | |
1022 | set-manager"). By default, Open vSwitch assumes that managers need | |
1023 | in-band rules set up on every bridge. You can disable these rules | |
1024 | on bridge br0 with: | |
1025 | ||
1026 | ovs-vsctl set bridge br0 other-config:disable-in-band=true | |
1027 | ||
1028 | This actually disables in-band control entirely for the bridge, as | |
1029 | if all the bridge's controllers were configured for out-of-band | |
1030 | control. | |
1031 | ||
1032 | Q: My OpenFlow controller doesn't see the VLANs that I expect. | |
1033 | ||
1034 | A: See answer under "VLANs", above. | |
1035 | ||
5cb2356b BP |
1036 | Q: I ran "ovs-ofctl add-flow br0 nw_dst=192.168.0.1,actions=drop" |
1037 | but I got a funny message like this: | |
1038 | ||
1039 | ofp_util|INFO|normalization changed ofp_match, details: | |
1040 | ofp_util|INFO| pre: nw_dst=192.168.0.1 | |
1041 | ofp_util|INFO|post: | |
1042 | ||
1043 | and when I ran "ovs-ofctl dump-flows br0" I saw that my nw_dst | |
1044 | match had disappeared, so that the flow ends up matching every | |
1045 | packet. | |
1046 | ||
1047 | A: The term "normalization" in the log message means that a flow | |
1048 | cannot match on an L3 field without saying what L3 protocol is in | |
1049 | use. The "ovs-ofctl" command above didn't specify an L3 protocol, | |
1050 | so the L3 field match was dropped. | |
1051 | ||
1052 | In this case, the L3 protocol could be IP or ARP. A correct | |
1053 | command for each possibility is, respectively: | |
1054 | ||
1055 | ovs-ofctl add-flow br0 ip,nw_dst=192.168.0.1,actions=drop | |
1056 | ||
1057 | and | |
1058 | ||
1059 | ovs-ofctl add-flow br0 arp,nw_dst=192.168.0.1,actions=drop | |
1060 | ||
1061 | Similarly, a flow cannot match on an L4 field without saying what | |
1062 | L4 protocol is in use. For example, the flow match "tp_src=1234" | |
1063 | is, by itself, meaningless and will be ignored. Instead, to match | |
1064 | TCP source port 1234, write "tcp,tp_src=1234", or to match UDP | |
1065 | source port 1234, write "udp,tp_src=1234". | |
1066 | ||
c5b25863 BP |
1067 | Q: How can I figure out the OpenFlow port number for a given port? |
1068 | ||
1069 | A: The OFPT_FEATURES_REQUEST message requests an OpenFlow switch to | |
1070 | respond with an OFPT_FEATURES_REPLY that, among other information, | |
1071 | includes a mapping between OpenFlow port names and numbers. From a | |
1072 | command prompt, "ovs-ofctl show br0" makes such a request and | |
1073 | prints the response for switch br0. | |
1074 | ||
1075 | The Interface table in the Open vSwitch database also maps OpenFlow | |
1076 | port names to numbers. To print the OpenFlow port number | |
1077 | associated with interface eth0, run: | |
1078 | ||
1079 | ovs-vsctl get Interface eth0 ofport | |
1080 | ||
1081 | You can print the entire mapping with: | |
1082 | ||
1083 | ovs-vsctl -- --columns=name,ofport list Interface | |
1084 | ||
1085 | but the output mixes together interfaces from all bridges in the | |
1086 | database, so it may be confusing if more than one bridge exists. | |
1087 | ||
1088 | In the Open vSwitch database, ofport value -1 means that the | |
1089 | interface could not be created due to an error. (The Open vSwitch | |
1090 | log should indicate the reason.) ofport value [] (the empty set) | |
1091 | means that the interface hasn't been created yet. The latter is | |
1092 | normally an intermittent condition (unless ovs-vswitchd is not | |
1093 | running). | |
7b287e99 | 1094 | |
af1ac4b9 BP |
1095 | Q: I added some flows with my controller or with ovs-ofctl, but when I |
1096 | run "ovs-dpctl dump-flows" I don't see them. | |
1097 | ||
1098 | A: ovs-dpctl queries a kernel datapath, not an OpenFlow switch. It | |
1099 | won't display the information that you want. You want to use | |
1100 | "ovs-ofctl dump-flows" instead. | |
1101 | ||
15d63ed3 BP |
1102 | Q: It looks like each of the interfaces in my bonded port shows up |
1103 | as an individual OpenFlow port. Is that right? | |
1104 | ||
1105 | A: Yes, Open vSwitch makes individual bond interfaces visible as | |
1106 | OpenFlow ports, rather than the bond as a whole. The interfaces | |
1107 | are treated together as a bond for only a few purposes: | |
1108 | ||
1109 | - Sending a packet to the OFPP_NORMAL port. (When an OpenFlow | |
1110 | controller is not configured, this happens implicitly to | |
1111 | every packet.) | |
1112 | ||
15d63ed3 BP |
1113 | - Mirrors configured for output to a bonded port. |
1114 | ||
1115 | It would make a lot of sense for Open vSwitch to present a bond as | |
1116 | a single OpenFlow port. If you want to contribute an | |
1117 | implementation of such a feature, please bring it up on the Open | |
1118 | vSwitch development mailing list at dev@openvswitch.org. | |
1119 | ||
bb955418 BP |
1120 | Q: I have a sophisticated network setup involving Open vSwitch, VMs or |
1121 | multiple hosts, and other components. The behavior isn't what I | |
1122 | expect. Help! | |
1123 | ||
1124 | A: To debug network behavior problems, trace the path of a packet, | |
1125 | hop-by-hop, from its origin in one host to a remote host. If | |
1126 | that's correct, then trace the path of the response packet back to | |
1127 | the origin. | |
1128 | ||
1129 | Usually a simple ICMP echo request and reply ("ping") packet is | |
1130 | good enough. Start by initiating an ongoing "ping" from the origin | |
1131 | host to a remote host. If you are tracking down a connectivity | |
1132 | problem, the "ping" will not display any successful output, but | |
1133 | packets are still being sent. (In this case the packets being sent | |
1134 | are likely ARP rather than ICMP.) | |
1135 | ||
1136 | Tools available for tracing include the following: | |
1137 | ||
1138 | - "tcpdump" and "wireshark" for observing hops across network | |
1139 | devices, such as Open vSwitch internal devices and physical | |
1140 | wires. | |
1141 | ||
1142 | - "ovs-appctl dpif/dump-flows <br>" in Open vSwitch 1.10 and | |
1143 | later or "ovs-dpctl dump-flows <br>" in earlier versions. | |
1144 | These tools allow one to observe the actions being taken on | |
1145 | packets in ongoing flows. | |
1146 | ||
1147 | See ovs-vswitchd(8) for "ovs-appctl dpif/dump-flows" | |
1148 | documentation, ovs-dpctl(8) for "ovs-dpctl dump-flows" | |
1149 | documentation, and "Why are there so many different ways to | |
1150 | dump flows?" above for some background. | |
1151 | ||
1152 | - "ovs-appctl ofproto/trace" to observe the logic behind how | |
1153 | ovs-vswitchd treats packets. See ovs-vswitchd(8) for | |
1154 | documentation. You can out more details about a given flow | |
1155 | that "ovs-dpctl dump-flows" displays, by cutting and pasting | |
1156 | a flow from the output into an "ovs-appctl ofproto/trace" | |
1157 | command. | |
1158 | ||
1159 | - SPAN, RSPAN, and ERSPAN features of physical switches, to | |
1160 | observe what goes on at these physical hops. | |
1161 | ||
1162 | Starting at the origin of a given packet, observe the packet at | |
1163 | each hop in turn. For example, in one plausible scenario, you | |
1164 | might: | |
1165 | ||
1166 | 1. "tcpdump" the "eth" interface through which an ARP egresses | |
1167 | a VM, from inside the VM. | |
1168 | ||
1169 | 2. "tcpdump" the "vif" or "tap" interface through which the ARP | |
1170 | ingresses the host machine. | |
1171 | ||
1172 | 3. Use "ovs-dpctl dump-flows" to spot the ARP flow and observe | |
1173 | the host interface through which the ARP egresses the | |
1174 | physical machine. You may need to use "ovs-dpctl show" to | |
1175 | interpret the port numbers. If the output seems surprising, | |
1176 | you can use "ovs-appctl ofproto/trace" to observe details of | |
1177 | how ovs-vswitchd determined the actions in the "ovs-dpctl | |
1178 | dump-flows" output. | |
1179 | ||
1180 | 4. "tcpdump" the "eth" interface through which the ARP egresses | |
1181 | the physical machine. | |
1182 | ||
1183 | 5. "tcpdump" the "eth" interface through which the ARP | |
1184 | ingresses the physical machine, at the remote host that | |
1185 | receives the ARP. | |
1186 | ||
1187 | 6. Use "ovs-dpctl dump-flows" to spot the ARP flow on the | |
1188 | remote host that receives the ARP and observe the VM "vif" | |
1189 | or "tap" interface to which the flow is directed. Again, | |
1190 | "ovs-dpctl show" and "ovs-appctl ofproto/trace" might help. | |
1191 | ||
1192 | 7. "tcpdump" the "vif" or "tap" interface to which the ARP is | |
1193 | directed. | |
1194 | ||
1195 | 8. "tcpdump" the "eth" interface through which the ARP | |
1196 | ingresses a VM, from inside the VM. | |
1197 | ||
1198 | It is likely that during one of these steps you will figure out the | |
1199 | problem. If not, then follow the ARP reply back to the origin, in | |
1200 | reverse. | |
1201 | ||
0f5edef0 BP |
1202 | Q: How do I make a flow drop packets? |
1203 | ||
1204 | A: An empty set of actions causes a packet to be dropped. You can | |
1205 | specify an empty set of actions with "actions=" on the ovs-ofctl | |
1206 | command line. For example: | |
1207 | ||
1208 | ovs-ofctl add-flow br0 priority=65535,actions= | |
1209 | ||
1210 | would cause every packet entering switch br0 to be dropped. | |
1211 | ||
1212 | You can write "drop" explicitly if you like. The effect is the | |
1213 | same. Thus, the following command also causes every packet | |
1214 | entering switch br0 to be dropped: | |
1215 | ||
1216 | ovs-ofctl add-flow br0 priority=65535,actions=drop | |
1217 | ||
1218 | ||
c483d489 BP |
1219 | Contact |
1220 | ------- | |
1221 | ||
1222 | bugs@openvswitch.org | |
1223 | http://openvswitch.org/ |