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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 | |
12 | designed to be used as a vswitch in virtualized server environments. A | |
13 | vswitch forwards traffic between different VMs on the same physical host | |
14 | and also forwards traffic between VMs and the physical network. Open | |
15 | vSwitch supports standard management interfaces (e.g. sFlow, NetFlow, | |
16 | RSPAN, CLI), and is open to programmatic extension and control using | |
17 | OpenFlow and the OVSDB management protocol. | |
18 | ||
19 | Open vSwitch as designed to be compatible with modern switching | |
20 | chipsets. This means that it can be ported to existing high-fanout | |
21 | switches allowing the same flexible control of the physical | |
22 | infrastructure as the virtual infrastructure. It also means that | |
23 | Open vSwitch will be able to take advantage of on-NIC switching | |
24 | chipsets as their functionality matures. | |
25 | ||
26 | Q: What virtualization platforms can use Open vSwitch? | |
27 | ||
28 | A: Open vSwitch can currently run on any Linux-based virtualization | |
29 | platform (kernel 2.6.18 and newer), including: KVM, VirtualBox, Xen, | |
30 | Xen Cloud Platform, XenServer. As of Linux 3.3 it is part of the | |
31 | mainline kernel. The bulk of the code is written in platform- | |
32 | independent C and is easily ported to other environments. We welcome | |
33 | inquires about integrating Open vSwitch with other virtualization | |
34 | platforms. | |
35 | ||
36 | Q: How can I try Open vSwitch? | |
37 | ||
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38 | A: The Open vSwitch source code can be built on a Linux system. You can |
39 | build and experiment with Open vSwitch on any Linux machine. | |
40 | Packages for various Linux distributions are available on many | |
41 | platforms, including: Debian, Ubuntu, Fedora. | |
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42 | |
43 | You may also download and run a virtualization platform that already | |
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44 | has Open vSwitch integrated. For example, download a recent ISO for |
45 | XenServer or Xen Cloud Platform. Be aware that the version | |
46 | integrated with a particular platform may not be the most recent Open | |
47 | vSwitch release. | |
48 | ||
49 | Q: Does Open vSwitch only work on Linux? | |
50 | ||
51 | A: No, Open vSwitch has been ported to a number of different operating | |
52 | systems and hardware platforms. Most of the development work occurs | |
53 | on Linux, but the code should be portable to any POSIX system. We've | |
54 | seen Open vSwitch ported to a number of different platforms, | |
55 | including FreeBSD, Windows, and even non-POSIX embedded systems. | |
56 | ||
57 | By definition, the Open vSwitch Linux kernel module only works on | |
58 | Linux and will provide the highest performance. However, a userspace | |
59 | datapath is available that should be very portable. | |
60 | ||
61 | Q: What's involved with porting Open vSwitch to a new platform or | |
62 | switching ASIC? | |
63 | ||
64 | A: The PORTING document describes how one would go about porting Open | |
65 | vSwitch to a new operating system or hardware platform. | |
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66 | |
67 | Q: Why would I use Open vSwitch instead of the Linux bridge? | |
68 | ||
69 | A: Open vSwitch is specially designed to make it easier to manage VM | |
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70 | network configuration and monitor state spread across many physical |
71 | hosts in dynamic virtualized environments. Please see WHY-OVS for a | |
72 | more detailed description of how Open vSwitch relates to the Linux | |
73 | Bridge. | |
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74 | |
75 | Q: How is Open vSwitch related to distributed virtual switches like the | |
76 | VMware vNetwork distributed switch or the Cisco Nexus 1000V? | |
77 | ||
78 | A: Distributed vswitch applications (e.g., VMware vNetwork distributed | |
79 | switch, Cisco Nexus 1000V) provide a centralized way to configure and | |
80 | monitor the network state of VMs that are spread across many physical | |
81 | hosts. Open vSwitch is not a distributed vswitch itself, rather it | |
82 | runs on each physical host and supports remote management in a way | |
83 | that makes it easier for developers of virtualization/cloud | |
84 | management platforms to offer distributed vswitch capabilities. | |
85 | ||
86 | To aid in distribution, Open vSwitch provides two open protocols that | |
87 | are specially designed for remote management in virtualized network | |
88 | environments: OpenFlow, which exposes flow-based forwarding state, | |
89 | and the OVSDB management protocol, which exposes switch port state. | |
90 | In addition to the switch implementation itself, Open vSwitch | |
91 | includes tools (ovs-controller, ovs-ofctl, ovs-vsctl) that developers | |
92 | can script and extend to provide distributed vswitch capabilities | |
93 | that are closely integrated with their virtualization management | |
94 | platform. | |
95 | ||
96 | Q: Why doesn't Open vSwitch support distribution? | |
97 | ||
98 | A: Open vSwitch is intended to be a useful component for building | |
99 | flexible network infrastructure. There are many different approaches | |
100 | to distribution which balance trade-offs between simplicity, | |
101 | scalability, hardware compatibility, convergence times, logical | |
102 | forwarding model, etc. The goal of Open vSwitch is to be able to | |
103 | support all as a primitive building block rather than choose a | |
104 | particular point in the distributed design space. | |
105 | ||
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106 | Q: How can I contribute to the Open vSwitch Community? |
107 | ||
108 | A: You can start by joining the mailing lists and helping to answer | |
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109 | questions. You can also suggest improvements to documentation. If |
110 | you have a feature or bug you would like to work on, send a mail to | |
111 | one of the mailing lists: | |
112 | ||
113 | http://openvswitch.org/mlists/ | |
114 | ||
115 | ||
116 | ||
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 | |
129 | 1.4.x. | |
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 | |
150 | Open vSwitch userspace should also work with the Linux kernel module | |
151 | built into Linux 3.3 and later. | |
152 | ||
153 | Open vSwitch userspace is not sensitive to the Linux kernel version. | |
154 | It should build against almost any kernel, certainly against 2.6.18 | |
155 | and later. | |
156 | ||
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157 | Q: What features are not available in the Open vSwitch kernel datapath |
158 | that ships as part of the upstream Linux kernel? | |
159 | ||
160 | A: The kernel module in upstream Linux 3.3 and later does not include | |
161 | the following features: | |
162 | ||
6302c641 BP |
163 | - Tunnel virtual ports, that is, interfaces with type "gre", |
164 | "ipsec_gre", "capwap". It is possible to create tunnels in | |
165 | Linux and attach them to Open vSwitch as system devices. | |
166 | However, they cannot be dynamically created through the OVSDB | |
167 | protocol or set the tunnel ids as a flow action. | |
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168 | |
169 | Work is in progress in adding these features to the upstream | |
170 | Linux version of the Open vSwitch kernel module. For now, if | |
171 | you need these features, use the kernel module from the Open | |
172 | vSwitch distribution instead of the upstream Linux kernel | |
173 | module. | |
174 | ||
6302c641 BP |
175 | - Patch virtual ports, that is, interfaces with type "patch". |
176 | You can use Linux "veth" devices as a substitute. | |
177 | ||
178 | We don't have any plans to add patch ports upstream. | |
179 | ||
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180 | Q: What features are not available when using the userspace datapath? |
181 | ||
182 | A: Tunnel and patch virtual ports are not supported, as described in the | |
183 | previous answer. It is also not possible to use queue-related | |
184 | actions. On Linux kernels before 2.6.39, maximum-sized VLAN packets | |
185 | may not be transmitted. | |
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186 | |
187 | ||
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188 | Terminology |
189 | ----------- | |
190 | ||
191 | Q: I thought Open vSwitch was a virtual Ethernet switch, but the | |
192 | documentation keeps talking about bridges. What's a bridge? | |
193 | ||
194 | A: In networking, the terms "bridge" and "switch" are synonyms. Open | |
195 | vSwitch implements an Ethernet switch, which means that it is also | |
196 | an Ethernet bridge. | |
197 | ||
198 | Q: What's a VLAN? | |
199 | ||
200 | A: See the "VLAN" section below. | |
201 | ||
202 | ||
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203 | Basic Configuration |
204 | ------------------- | |
205 | ||
206 | Q: How do I configure a port as an access port? | |
207 | ||
208 | A: Add "tag=VLAN" to your "ovs-vsctl add-port" command. For example, | |
209 | the following commands configure br0 with eth0 as a trunk port (the | |
210 | default) and tap0 as an access port for VLAN 9: | |
211 | ||
212 | ovs-vsctl add-br br0 | |
213 | ovs-vsctl add-port br0 eth0 | |
214 | ovs-vsctl add-port br0 tap0 tag=9 | |
215 | ||
216 | If you want to configure an already added port as an access port, | |
217 | use "ovs-vsctl set", e.g.: | |
218 | ||
219 | ovs-vsctl set port tap0 tag=9 | |
220 | ||
221 | Q: How do I configure a port as a SPAN port, that is, enable mirroring | |
222 | of all traffic to that port? | |
223 | ||
224 | A: The following commands configure br0 with eth0 and tap0 as trunk | |
225 | ports. All traffic coming in or going out on eth0 or tap0 is also | |
226 | mirrored to tap1; any traffic arriving on tap1 is dropped: | |
227 | ||
228 | ovs-vsctl add-br br0 | |
229 | ovs-vsctl add-port br0 eth0 | |
230 | ovs-vsctl add-port br0 tap0 | |
231 | ovs-vsctl add-port br0 tap1 \ | |
232 | -- --id=@p get port tap1 \ | |
233 | -- --id=@m create mirror name=m0 select-all=true output-port=@p \ | |
234 | -- set bridge br0 mirrors=@m | |
235 | ||
236 | To later disable mirroring, run: | |
237 | ||
238 | ovs-vsctl clear bridge br0 mirrors | |
239 | ||
240 | Q: How do I configure a VLAN as an RSPAN VLAN, that is, enable | |
241 | mirroring of all traffic to that VLAN? | |
242 | ||
243 | A: The following commands configure br0 with eth0 as a trunk port and | |
244 | tap0 as an access port for VLAN 10. All traffic coming in or going | |
245 | out on tap0, as well as traffic coming in or going out on eth0 in | |
246 | VLAN 10, is also mirrored to VLAN 15 on eth0. The original tag for | |
247 | VLAN 10, in cases where one is present, is dropped as part of | |
248 | mirroring: | |
249 | ||
250 | ovs-vsctl add-br br0 | |
251 | ovs-vsctl add-port br0 eth0 | |
252 | ovs-vsctl add-port br0 tap0 tag=10 | |
253 | ovs-vsctl \ | |
254 | -- --id=@m create mirror name=m0 select-all=true select-vlan=10 \ | |
255 | output-vlan=15 \ | |
256 | -- set bridge br0 mirrors=@m | |
257 | ||
258 | To later disable mirroring, run: | |
259 | ||
260 | ovs-vsctl clear bridge br0 mirrors | |
261 | ||
262 | Mirroring to a VLAN can disrupt a network that contains unmanaged | |
263 | switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a | |
264 | GRE tunnel has fewer caveats than mirroring to a VLAN and should | |
265 | generally be preferred. | |
266 | ||
267 | Q: Can I mirror more than one input VLAN to an RSPAN VLAN? | |
268 | ||
269 | A: Yes, but mirroring to a VLAN strips the original VLAN tag in favor | |
270 | of the specified output-vlan. This loss of information may make | |
271 | the mirrored traffic too hard to interpret. | |
272 | ||
273 | To mirror multiple VLANs, use the commands above, but specify a | |
274 | comma-separated list of VLANs as the value for select-vlan. To | |
275 | mirror every VLAN, use the commands above, but omit select-vlan and | |
276 | its value entirely. | |
277 | ||
278 | When a packet arrives on a VLAN that is used as a mirror output | |
279 | VLAN, the mirror is disregarded. Instead, in standalone mode, OVS | |
280 | floods the packet across all the ports for which the mirror output | |
281 | VLAN is configured. (If an OpenFlow controller is in use, then it | |
282 | can override this behavior through the flow table.) If OVS is used | |
283 | as an intermediate switch, rather than an edge switch, this ensures | |
284 | that the RSPAN traffic is distributed through the network. | |
285 | ||
286 | Mirroring to a VLAN can disrupt a network that contains unmanaged | |
287 | switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a | |
288 | GRE tunnel has fewer caveats than mirroring to a VLAN and should | |
289 | generally be preferred. | |
290 | ||
291 | Q: How do I configure mirroring of all traffic to a GRE tunnel? | |
292 | ||
293 | A: The following commands configure br0 with eth0 and tap0 as trunk | |
294 | ports. All traffic coming in or going out on eth0 or tap0 is also | |
295 | mirrored to gre0, a GRE tunnel to the remote host 192.168.1.10; any | |
296 | traffic arriving on gre0 is dropped: | |
297 | ||
298 | ovs-vsctl add-br br0 | |
299 | ovs-vsctl add-port br0 eth0 | |
300 | ovs-vsctl add-port br0 tap0 | |
301 | ovs-vsctl add-port br0 gre0 \ | |
302 | -- set interface gre0 type=gre options:remote_ip=192.168.1.10 \ | |
303 | -- --id=@p get port gre0 \ | |
304 | -- --id=@m create mirror name=m0 select-all=true output-port=@p \ | |
305 | -- set bridge br0 mirrors=@m | |
306 | ||
307 | To later disable mirroring and destroy the GRE tunnel: | |
308 | ||
309 | ovs-vsctl clear bridge br0 mirrors | |
310 | ovs-vcstl del-port br0 gre0 | |
311 | ||
312 | Q: Does Open vSwitch support ERSPAN? | |
313 | ||
314 | A: No. ERSPAN is an undocumented proprietary protocol. As an | |
315 | alternative, Open vSwitch supports mirroring to a GRE tunnel (see | |
316 | above). | |
317 | ||
318 | ||
c483d489 BP |
319 | Configuration Problems |
320 | ---------------------- | |
321 | ||
322 | Q: I created a bridge and added my Ethernet port to it, using commands | |
323 | like these: | |
324 | ||
325 | ovs-vsctl add-br br0 | |
326 | ovs-vsctl add-port br0 eth0 | |
327 | ||
328 | and as soon as I ran the "add-port" command I lost all connectivity | |
329 | through eth0. Help! | |
330 | ||
331 | A: A physical Ethernet device that is part of an Open vSwitch bridge | |
332 | should not have an IP address. If one does, then that IP address | |
333 | will not be fully functional. | |
334 | ||
335 | You can restore functionality by moving the IP address to an Open | |
336 | vSwitch "internal" device, such as the network device named after | |
337 | the bridge itself. For example, assuming that eth0's IP address is | |
338 | 192.168.128.5, you could run the commands below to fix up the | |
339 | situation: | |
340 | ||
341 | ifconfig eth0 0.0.0.0 | |
342 | ifconfig br0 192.168.128.5 | |
343 | ||
344 | (If your only connection to the machine running OVS is through the | |
345 | IP address in question, then you would want to run all of these | |
346 | commands on a single command line, or put them into a script.) If | |
347 | there were any additional routes assigned to eth0, then you would | |
348 | also want to use commands to adjust these routes to go through br0. | |
349 | ||
350 | If you use DHCP to obtain an IP address, then you should kill the | |
351 | DHCP client that was listening on the physical Ethernet interface | |
352 | (e.g. eth0) and start one listening on the internal interface | |
353 | (e.g. br0). You might still need to manually clear the IP address | |
354 | from the physical interface (e.g. with "ifconfig eth0 0.0.0.0"). | |
355 | ||
356 | There is no compelling reason why Open vSwitch must work this way. | |
357 | However, this is the way that the Linux kernel bridge module has | |
358 | always worked, so it's a model that those accustomed to Linux | |
359 | bridging are already used to. Also, the model that most people | |
360 | expect is not implementable without kernel changes on all the | |
361 | versions of Linux that Open vSwitch supports. | |
362 | ||
363 | By the way, this issue is not specific to physical Ethernet | |
364 | devices. It applies to all network devices except Open vswitch | |
365 | "internal" devices. | |
366 | ||
367 | Q: I created a bridge and added a couple of Ethernet ports to it, | |
368 | using commands like these: | |
369 | ||
370 | ovs-vsctl add-br br0 | |
371 | ovs-vsctl add-port br0 eth0 | |
372 | ovs-vsctl add-port br0 eth1 | |
373 | ||
374 | and now my network seems to have melted: connectivity is unreliable | |
375 | (even connectivity that doesn't go through Open vSwitch), all the | |
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376 | LEDs on my physical switches are blinking, wireshark shows |
377 | duplicated packets, and CPU usage is very high. | |
c483d489 BP |
378 | |
379 | A: More than likely, you've looped your network. Probably, eth0 and | |
380 | eth1 are connected to the same physical Ethernet switch. This | |
381 | yields a scenario where OVS receives a broadcast packet on eth0 and | |
382 | sends it out on eth1, then the physical switch connected to eth1 | |
383 | sends the packet back on eth0, and so on forever. More complicated | |
384 | scenarios, involving a loop through multiple switches, are possible | |
385 | too. | |
386 | ||
387 | The solution depends on what you are trying to do: | |
388 | ||
389 | - If you added eth0 and eth1 to get higher bandwidth or higher | |
390 | reliability between OVS and your physical Ethernet switch, | |
391 | use a bond. The following commands create br0 and then add | |
392 | eth0 and eth1 as a bond: | |
393 | ||
394 | ovs-vsctl add-br br0 | |
395 | ovs-vsctl add-bond br0 bond0 eth0 eth1 | |
396 | ||
397 | Bonds have tons of configuration options. Please read the | |
398 | documentation on the Port table in ovs-vswitchd.conf.db(5) | |
399 | for all the details. | |
400 | ||
401 | - Perhaps you don't actually need eth0 and eth1 to be on the | |
402 | same bridge. For example, if you simply want to be able to | |
403 | connect each of them to virtual machines, then you can put | |
404 | each of them on a bridge of its own: | |
405 | ||
406 | ovs-vsctl add-br br0 | |
407 | ovs-vsctl add-port br0 eth0 | |
408 | ||
409 | ovs-vsctl add-br br1 | |
410 | ovs-vsctl add-port br1 eth1 | |
411 | ||
412 | and then connect VMs to br0 and br1. (A potential | |
413 | disadvantage is that traffic cannot directly pass between br0 | |
414 | and br1. Instead, it will go out eth0 and come back in eth1, | |
415 | or vice versa.) | |
416 | ||
417 | - If you have a redundant or complex network topology and you | |
418 | want to prevent loops, turn on spanning tree protocol (STP). | |
419 | The following commands create br0, enable STP, and add eth0 | |
420 | and eth1 to the bridge. The order is important because you | |
421 | don't want have to have a loop in your network even | |
422 | transiently: | |
423 | ||
424 | ovs-vsctl add-br br0 | |
425 | ovs-vsctl set bridge br0 stp_enable=true | |
426 | ovs-vsctl add-port br0 eth0 | |
427 | ovs-vsctl add-port br0 eth1 | |
428 | ||
429 | The Open vSwitch implementation of STP is not well tested. | |
430 | Please report any bugs you observe, but if you'd rather avoid | |
431 | acting as a beta tester then another option might be your | |
432 | best shot. | |
433 | ||
434 | Q: I can't seem to use Open vSwitch in a wireless network. | |
435 | ||
436 | A: Wireless base stations generally only allow packets with the source | |
437 | MAC address of NIC that completed the initial handshake. | |
438 | Therefore, without MAC rewriting, only a single device can | |
439 | communicate over a single wireless link. | |
440 | ||
441 | This isn't specific to Open vSwitch, it's enforced by the access | |
442 | point, so the same problems will show up with the Linux bridge or | |
443 | any other way to do bridging. | |
444 | ||
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445 | Q: Is there any documentation on the database tables and fields? |
446 | ||
447 | A: Yes. ovs-vswitchd.conf.db(5) is a comprehensive reference. | |
448 | ||
acf60855 JP |
449 | Q: When I run ovs-dpctl I no longer see the bridges I created. Instead, |
450 | I only see a datapath called "ovs-system". How can I see datapath | |
451 | information about a particular bridge? | |
452 | ||
453 | A: In version 1.9.0, OVS switched to using a single datapath that is | |
454 | shared by all bridges of that type. The "ovs-appctl dpif/*" | |
455 | commands provide similar functionality that is scoped by the bridge. | |
456 | ||
c483d489 BP |
457 | |
458 | VLANs | |
459 | ----- | |
460 | ||
14481051 BP |
461 | Q: What's a VLAN? |
462 | ||
463 | A: At the simplest level, a VLAN (short for "virtual LAN") is a way to | |
464 | partition a single switch into multiple switches. Suppose, for | |
465 | example, that you have two groups of machines, group A and group B. | |
466 | You want the machines in group A to be able to talk to each other, | |
467 | and you want the machine in group B to be able to talk to each | |
468 | other, but you don't want the machines in group A to be able to | |
469 | talk to the machines in group B. You can do this with two | |
470 | switches, by plugging the machines in group A into one switch and | |
471 | the machines in group B into the other switch. | |
472 | ||
473 | If you only have one switch, then you can use VLANs to do the same | |
474 | thing, by configuring the ports for machines in group A as VLAN | |
475 | "access ports" for one VLAN and the ports for group B as "access | |
476 | ports" for a different VLAN. The switch will only forward packets | |
477 | between ports that are assigned to the same VLAN, so this | |
478 | effectively subdivides your single switch into two independent | |
479 | switches, one for each group of machines. | |
480 | ||
481 | So far we haven't said anything about VLAN headers. With access | |
482 | ports, like we've described so far, no VLAN header is present in | |
483 | the Ethernet frame. This means that the machines (or switches) | |
484 | connected to access ports need not be aware that VLANs are | |
485 | involved, just like in the case where we use two different physical | |
486 | switches. | |
487 | ||
488 | Now suppose that you have a whole bunch of switches in your | |
489 | network, instead of just one, and that some machines in group A are | |
490 | connected directly to both switches 1 and 2. To allow these | |
491 | machines to talk to each other, you could add an access port for | |
492 | group A's VLAN to switch 1 and another to switch 2, and then | |
493 | connect an Ethernet cable between those ports. That works fine, | |
494 | but it doesn't scale well as the number of switches and the number | |
495 | of VLANs increases, because you use up a lot of valuable switch | |
496 | ports just connecting together your VLANs. | |
497 | ||
498 | This is where VLAN headers come in. Instead of using one cable and | |
499 | two ports per VLAN to connect a pair of switches, we configure a | |
500 | port on each switch as a VLAN "trunk port". Packets sent and | |
501 | received on a trunk port carry a VLAN header that says what VLAN | |
502 | the packet belongs to, so that only two ports total are required to | |
503 | connect the switches, regardless of the number of VLANs in use. | |
504 | Normally, only switches (either physical or virtual) are connected | |
505 | to a trunk port, not individual hosts, because individual hosts | |
506 | don't expect to see a VLAN header in the traffic that they receive. | |
507 | ||
508 | None of the above discussion says anything about particular VLAN | |
509 | numbers. This is because VLAN numbers are completely arbitrary. | |
510 | One must only ensure that a given VLAN is numbered consistently | |
511 | throughout a network and that different VLANs are given different | |
512 | numbers. (That said, VLAN 0 is usually synonymous with a packet | |
513 | that has no VLAN header, and VLAN 4095 is reserved.) | |
514 | ||
c483d489 BP |
515 | Q: VLANs don't work. |
516 | ||
517 | A: Many drivers in Linux kernels before version 3.3 had VLAN-related | |
518 | bugs. If you are having problems with VLANs that you suspect to be | |
519 | driver related, then you have several options: | |
520 | ||
521 | - Upgrade to Linux 3.3 or later. | |
522 | ||
523 | - Build and install a fixed version of the particular driver | |
524 | that is causing trouble, if one is available. | |
525 | ||
526 | - Use a NIC whose driver does not have VLAN problems. | |
527 | ||
528 | - Use "VLAN splinters", a feature in Open vSwitch 1.4 and later | |
529 | that works around bugs in kernel drivers. To enable VLAN | |
530 | splinters on interface eth0, use the command: | |
531 | ||
7b287e99 | 532 | ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true |
c483d489 BP |
533 | |
534 | For VLAN splinters to be effective, Open vSwitch must know | |
535 | which VLANs are in use. See the "VLAN splinters" section in | |
536 | the Interface table in ovs-vswitchd.conf.db(5) for details on | |
537 | how Open vSwitch infers in-use VLANs. | |
538 | ||
539 | VLAN splinters increase memory use and reduce performance, so | |
540 | use them only if needed. | |
541 | ||
542 | - Apply the "vlan workaround" patch from the XenServer kernel | |
543 | patch queue, build Open vSwitch against this patched kernel, | |
544 | and then use ovs-vlan-bug-workaround(8) to enable the VLAN | |
545 | workaround for each interface whose driver is buggy. | |
546 | ||
547 | (This is a nontrivial exercise, so this option is included | |
548 | only for completeness.) | |
549 | ||
550 | It is not always easy to tell whether a Linux kernel driver has | |
551 | buggy VLAN support. The ovs-vlan-test(8) and ovs-test(8) utilities | |
552 | can help you test. See their manpages for details. Of the two | |
553 | utilities, ovs-test(8) is newer and more thorough, but | |
554 | ovs-vlan-test(8) may be easier to use. | |
555 | ||
556 | Q: VLANs still don't work. I've tested the driver so I know that it's OK. | |
557 | ||
558 | A: Do you have VLANs enabled on the physical switch that OVS is | |
559 | attached to? Make sure that the port is configured to trunk the | |
560 | VLAN or VLANs that you are using with OVS. | |
561 | ||
562 | Q: Outgoing VLAN-tagged traffic goes through OVS to my physical switch | |
563 | and to its destination host, but OVS seems to drop incoming return | |
564 | traffic. | |
565 | ||
566 | A: It's possible that you have the VLAN configured on your physical | |
567 | switch as the "native" VLAN. In this mode, the switch treats | |
568 | incoming packets either tagged with the native VLAN or untagged as | |
569 | part of the native VLAN. It may also send outgoing packets in the | |
570 | native VLAN without a VLAN tag. | |
571 | ||
572 | If this is the case, you have two choices: | |
573 | ||
574 | - Change the physical switch port configuration to tag packets | |
575 | it forwards to OVS with the native VLAN instead of forwarding | |
576 | them untagged. | |
577 | ||
578 | - Change the OVS configuration for the physical port to a | |
579 | native VLAN mode. For example, the following sets up a | |
580 | bridge with port eth0 in "native-tagged" mode in VLAN 9: | |
581 | ||
582 | ovs-vsctl add-br br0 | |
583 | ovs-vsctl add-port br0 eth0 tag=9 vlan_mode=native-tagged | |
584 | ||
585 | In this situation, "native-untagged" mode will probably work | |
586 | equally well. Refer to the documentation for the Port table | |
587 | in ovs-vswitchd.conf.db(5) for more information. | |
588 | ||
8d45e938 BP |
589 | Q: I added a pair of VMs on different VLANs, like this: |
590 | ||
591 | ovs-vsctl add-br br0 | |
592 | ovs-vsctl add-port br0 eth0 | |
593 | ovs-vsctl add-port br0 tap0 tag=9 | |
594 | ovs-vsctl add-port br0 tap1 tag=10 | |
595 | ||
596 | but the VMs can't access each other, the external network, or the | |
597 | Internet. | |
598 | ||
599 | A: It is to be expected that the VMs can't access each other. VLANs | |
600 | are a means to partition a network. When you configured tap0 and | |
601 | tap1 as access ports for different VLANs, you indicated that they | |
602 | should be isolated from each other. | |
603 | ||
604 | As for the external network and the Internet, it seems likely that | |
605 | the machines you are trying to access are not on VLAN 9 (or 10) and | |
606 | that the Internet is not available on VLAN 9 (or 10). | |
607 | ||
c483d489 BP |
608 | Q: Can I configure an IP address on a VLAN? |
609 | ||
610 | A: Yes. Use an "internal port" configured as an access port. For | |
611 | example, the following configures IP address 192.168.0.7 on VLAN 9. | |
612 | That is, OVS will forward packets from eth0 to 192.168.0.7 only if | |
613 | they have an 802.1Q header with VLAN 9. Conversely, traffic | |
614 | forwarded from 192.168.0.7 to eth0 will be tagged with an 802.1Q | |
615 | header with VLAN 9: | |
616 | ||
617 | ovs-vsctl add-br br0 | |
618 | ovs-vsctl add-port br0 eth0 | |
619 | ovs-vsctl add-port br0 vlan9 tag=9 -- set interface vlan9 type=internal | |
620 | ifconfig vlan9 192.168.0.7 | |
621 | ||
622 | Q: My OpenFlow controller doesn't see the VLANs that I expect. | |
623 | ||
624 | A: The configuration for VLANs in the Open vSwitch database (e.g. via | |
625 | ovs-vsctl) only affects traffic that goes through Open vSwitch's | |
626 | implementation of the OpenFlow "normal switching" action. By | |
627 | default, when Open vSwitch isn't connected to a controller and | |
628 | nothing has been manually configured in the flow table, all traffic | |
629 | goes through the "normal switching" action. But, if you set up | |
630 | OpenFlow flows on your own, through a controller or using ovs-ofctl | |
631 | or through other means, then you have to implement VLAN handling | |
632 | yourself. | |
633 | ||
634 | You can use "normal switching" as a component of your OpenFlow | |
635 | actions, e.g. by putting "normal" into the lists of actions on | |
636 | ovs-ofctl or by outputting to OFPP_NORMAL from an OpenFlow | |
637 | controller. This will only be suitable for some situations, | |
638 | though. | |
639 | ||
f0a0c1a6 BP |
640 | Q: I configured ports on a bridge as access ports with different VLAN |
641 | tags, like this: | |
642 | ||
643 | ovs-vsctl add-br br0 | |
644 | ovs-vsctl set-controller br0 tcp:192.168.0.10:6633 | |
645 | ovs-vsctl add-port br0 eth0 | |
646 | ovs-vsctl add-port br0 tap0 tag=9 | |
647 | ovs-vsctl add-port br0 tap1 tag=10 | |
648 | ||
649 | but the VMs running behind tap0 and tap1 can still communicate, | |
650 | that is, they are not isolated from each other even though they are | |
651 | on different VLANs. | |
652 | ||
653 | A: Do you have a controller configured on br0 (as the commands above | |
654 | do)? If so, then this is a variant on the previous question, "My | |
655 | OpenFlow controller doesn't see the VLANs that I expect," and you | |
656 | can refer to the answer there for more information. | |
657 | ||
c483d489 BP |
658 | |
659 | Controllers | |
660 | ----------- | |
661 | ||
7b287e99 JP |
662 | Q: What versions of OpenFlow does Open vSwitch support? |
663 | ||
8e70e196 BP |
664 | A: Open vSwitch 1.9 and earlier support only OpenFlow 1.0 (plus |
665 | extensions that bring in many of the features from later versions | |
666 | of OpenFlow). | |
7b287e99 | 667 | |
8e70e196 BP |
668 | Open vSwitch versions 1.10 and later will have experimental support |
669 | for OpenFlow 1.2 and 1.3. On these versions of Open vSwitch, the | |
670 | following command enables OpenFlow 1.0, 1.2, and 1.3 on bridge br0: | |
671 | ||
672 | ovs-vsctl set bridge br0 protocols=openflow10,openflow12,openflow13 | |
673 | ||
674 | Support for OpenFlow 1.1 is incomplete enough that it cannot yet be | |
675 | enabled, even experimentally. | |
676 | ||
677 | Support for OpenFlow 1.2 and 1.3 is still incomplete. Work to be | |
678 | done is tracked in OPENFLOW-1.1+ in the Open vSwitch source tree | |
679 | (also via http://openvswitch.org/development/openflow-1-x-plan/). | |
680 | When support for a given OpenFlow version is solidly implemented, | |
681 | Open vSwitch will enable that version by default. | |
7b287e99 | 682 | |
c483d489 BP |
683 | Q: I'm getting "error type 45250 code 0". What's that? |
684 | ||
685 | A: This is a Open vSwitch extension to OpenFlow error codes. Open | |
686 | vSwitch uses this extension when it must report an error to an | |
687 | OpenFlow controller but no standard OpenFlow error code is | |
688 | suitable. | |
689 | ||
690 | Open vSwitch logs the errors that it sends to controllers, so the | |
691 | easiest thing to do is probably to look at the ovs-vswitchd log to | |
692 | find out what the error was. | |
693 | ||
694 | If you want to dissect the extended error message yourself, the | |
695 | format is documented in include/openflow/nicira-ext.h in the Open | |
696 | vSwitch source distribution. The extended error codes are | |
697 | documented in lib/ofp-errors.h. | |
698 | ||
699 | Q1: Some of the traffic that I'd expect my OpenFlow controller to see | |
700 | doesn't actually appear through the OpenFlow connection, even | |
701 | though I know that it's going through. | |
702 | Q2: Some of the OpenFlow flows that my controller sets up don't seem | |
703 | to apply to certain traffic, especially traffic between OVS and | |
704 | the controller itself. | |
705 | ||
706 | A: By default, Open vSwitch assumes that OpenFlow controllers are | |
707 | connected "in-band", that is, that the controllers are actually | |
708 | part of the network that is being controlled. In in-band mode, | |
709 | Open vSwitch sets up special "hidden" flows to make sure that | |
710 | traffic can make it back and forth between OVS and the controllers. | |
711 | These hidden flows are higher priority than any flows that can be | |
712 | set up through OpenFlow, and they are not visible through normal | |
713 | OpenFlow flow table dumps. | |
714 | ||
715 | Usually, the hidden flows are desirable and helpful, but | |
716 | occasionally they can cause unexpected behavior. You can view the | |
717 | full OpenFlow flow table, including hidden flows, on bridge br0 | |
718 | with the command: | |
719 | ||
720 | ovs-appctl bridge/dump-flows br0 | |
721 | ||
722 | to help you debug. The hidden flows are those with priorities | |
723 | greater than 65535 (the maximum priority that can be set with | |
724 | OpenFlow). | |
725 | ||
726 | The DESIGN file at the top level of the Open vSwitch source | |
727 | distribution describes the in-band model in detail. | |
728 | ||
729 | If your controllers are not actually in-band (e.g. they are on | |
730 | localhost via 127.0.0.1, or on a separate network), then you should | |
731 | configure your controllers in "out-of-band" mode. If you have one | |
732 | controller on bridge br0, then you can configure out-of-band mode | |
733 | on it with: | |
734 | ||
735 | ovs-vsctl set controller br0 connection-mode=out-of-band | |
736 | ||
737 | Q: I configured all my controllers for out-of-band control mode but | |
738 | "ovs-appctl bridge/dump-flows" still shows some hidden flows. | |
739 | ||
740 | A: You probably have a remote manager configured (e.g. with "ovs-vsctl | |
741 | set-manager"). By default, Open vSwitch assumes that managers need | |
742 | in-band rules set up on every bridge. You can disable these rules | |
743 | on bridge br0 with: | |
744 | ||
745 | ovs-vsctl set bridge br0 other-config:disable-in-band=true | |
746 | ||
747 | This actually disables in-band control entirely for the bridge, as | |
748 | if all the bridge's controllers were configured for out-of-band | |
749 | control. | |
750 | ||
751 | Q: My OpenFlow controller doesn't see the VLANs that I expect. | |
752 | ||
753 | A: See answer under "VLANs", above. | |
754 | ||
5cb2356b BP |
755 | Q: I ran "ovs-ofctl add-flow br0 nw_dst=192.168.0.1,actions=drop" |
756 | but I got a funny message like this: | |
757 | ||
758 | ofp_util|INFO|normalization changed ofp_match, details: | |
759 | ofp_util|INFO| pre: nw_dst=192.168.0.1 | |
760 | ofp_util|INFO|post: | |
761 | ||
762 | and when I ran "ovs-ofctl dump-flows br0" I saw that my nw_dst | |
763 | match had disappeared, so that the flow ends up matching every | |
764 | packet. | |
765 | ||
766 | A: The term "normalization" in the log message means that a flow | |
767 | cannot match on an L3 field without saying what L3 protocol is in | |
768 | use. The "ovs-ofctl" command above didn't specify an L3 protocol, | |
769 | so the L3 field match was dropped. | |
770 | ||
771 | In this case, the L3 protocol could be IP or ARP. A correct | |
772 | command for each possibility is, respectively: | |
773 | ||
774 | ovs-ofctl add-flow br0 ip,nw_dst=192.168.0.1,actions=drop | |
775 | ||
776 | and | |
777 | ||
778 | ovs-ofctl add-flow br0 arp,nw_dst=192.168.0.1,actions=drop | |
779 | ||
780 | Similarly, a flow cannot match on an L4 field without saying what | |
781 | L4 protocol is in use. For example, the flow match "tp_src=1234" | |
782 | is, by itself, meaningless and will be ignored. Instead, to match | |
783 | TCP source port 1234, write "tcp,tp_src=1234", or to match UDP | |
784 | source port 1234, write "udp,tp_src=1234". | |
785 | ||
c5b25863 BP |
786 | Q: How can I figure out the OpenFlow port number for a given port? |
787 | ||
788 | A: The OFPT_FEATURES_REQUEST message requests an OpenFlow switch to | |
789 | respond with an OFPT_FEATURES_REPLY that, among other information, | |
790 | includes a mapping between OpenFlow port names and numbers. From a | |
791 | command prompt, "ovs-ofctl show br0" makes such a request and | |
792 | prints the response for switch br0. | |
793 | ||
794 | The Interface table in the Open vSwitch database also maps OpenFlow | |
795 | port names to numbers. To print the OpenFlow port number | |
796 | associated with interface eth0, run: | |
797 | ||
798 | ovs-vsctl get Interface eth0 ofport | |
799 | ||
800 | You can print the entire mapping with: | |
801 | ||
802 | ovs-vsctl -- --columns=name,ofport list Interface | |
803 | ||
804 | but the output mixes together interfaces from all bridges in the | |
805 | database, so it may be confusing if more than one bridge exists. | |
806 | ||
807 | In the Open vSwitch database, ofport value -1 means that the | |
808 | interface could not be created due to an error. (The Open vSwitch | |
809 | log should indicate the reason.) ofport value [] (the empty set) | |
810 | means that the interface hasn't been created yet. The latter is | |
811 | normally an intermittent condition (unless ovs-vswitchd is not | |
812 | running). | |
7b287e99 | 813 | |
af1ac4b9 BP |
814 | Q: I added some flows with my controller or with ovs-ofctl, but when I |
815 | run "ovs-dpctl dump-flows" I don't see them. | |
816 | ||
817 | A: ovs-dpctl queries a kernel datapath, not an OpenFlow switch. It | |
818 | won't display the information that you want. You want to use | |
819 | "ovs-ofctl dump-flows" instead. | |
820 | ||
15d63ed3 BP |
821 | Q: It looks like each of the interfaces in my bonded port shows up |
822 | as an individual OpenFlow port. Is that right? | |
823 | ||
824 | A: Yes, Open vSwitch makes individual bond interfaces visible as | |
825 | OpenFlow ports, rather than the bond as a whole. The interfaces | |
826 | are treated together as a bond for only a few purposes: | |
827 | ||
828 | - Sending a packet to the OFPP_NORMAL port. (When an OpenFlow | |
829 | controller is not configured, this happens implicitly to | |
830 | every packet.) | |
831 | ||
832 | - The "autopath" Nicira extension action. However, "autopath" | |
833 | is deprecated and scheduled for removal in February 2013. | |
834 | ||
835 | - Mirrors configured for output to a bonded port. | |
836 | ||
837 | It would make a lot of sense for Open vSwitch to present a bond as | |
838 | a single OpenFlow port. If you want to contribute an | |
839 | implementation of such a feature, please bring it up on the Open | |
840 | vSwitch development mailing list at dev@openvswitch.org. | |
841 | ||
c483d489 BP |
842 | Contact |
843 | ------- | |
844 | ||
845 | bugs@openvswitch.org | |
846 | http://openvswitch.org/ |