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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 | |
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 | ||
131 | Q: What features are not available in the Open vSwitch kernel datapath | |
132 | that ships as part of the upstream Linux kernel? | |
133 | ||
134 | A: The kernel module in upstream Linux 3.3 and later does not include | |
135 | the following features: | |
136 | ||
137 | - Bridge compatibility, that is, support for the ovs-brcompatd | |
138 | daemon that (if you enable it) lets "brctl" and other Linux | |
139 | bridge tools transparently work with Open vSwitch instead. | |
140 | ||
141 | We do not expect bridge compatibility to ever be available in | |
142 | upstream Linux. If you need bridge compatibility, use the | |
143 | kernel module from the Open vSwitch distribution instead of the | |
144 | upstream Linux kernel module. | |
145 | ||
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146 | - Tunnel virtual ports, that is, interfaces with type "gre", |
147 | "ipsec_gre", "capwap". It is possible to create tunnels in | |
148 | Linux and attach them to Open vSwitch as system devices. | |
149 | However, they cannot be dynamically created through the OVSDB | |
150 | protocol or set the tunnel ids as a flow action. | |
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151 | |
152 | Work is in progress in adding these features to the upstream | |
153 | Linux version of the Open vSwitch kernel module. For now, if | |
154 | you need these features, use the kernel module from the Open | |
155 | vSwitch distribution instead of the upstream Linux kernel | |
156 | module. | |
157 | ||
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158 | - Patch virtual ports, that is, interfaces with type "patch". |
159 | You can use Linux "veth" devices as a substitute. | |
160 | ||
161 | We don't have any plans to add patch ports upstream. | |
162 | ||
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163 | Q: What features are not available when using the userspace datapath? |
164 | ||
165 | A: Tunnel and patch virtual ports are not supported, as described in the | |
166 | previous answer. It is also not possible to use queue-related | |
167 | actions. On Linux kernels before 2.6.39, maximum-sized VLAN packets | |
168 | may not be transmitted. | |
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169 | |
170 | ||
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171 | Basic Configuration |
172 | ------------------- | |
173 | ||
174 | Q: How do I configure a port as an access port? | |
175 | ||
176 | A: Add "tag=VLAN" to your "ovs-vsctl add-port" command. For example, | |
177 | the following commands configure br0 with eth0 as a trunk port (the | |
178 | default) and tap0 as an access port for VLAN 9: | |
179 | ||
180 | ovs-vsctl add-br br0 | |
181 | ovs-vsctl add-port br0 eth0 | |
182 | ovs-vsctl add-port br0 tap0 tag=9 | |
183 | ||
184 | If you want to configure an already added port as an access port, | |
185 | use "ovs-vsctl set", e.g.: | |
186 | ||
187 | ovs-vsctl set port tap0 tag=9 | |
188 | ||
189 | Q: How do I configure a port as a SPAN port, that is, enable mirroring | |
190 | of all traffic to that port? | |
191 | ||
192 | A: The following commands configure br0 with eth0 and tap0 as trunk | |
193 | ports. All traffic coming in or going out on eth0 or tap0 is also | |
194 | mirrored to tap1; any traffic arriving on tap1 is dropped: | |
195 | ||
196 | ovs-vsctl add-br br0 | |
197 | ovs-vsctl add-port br0 eth0 | |
198 | ovs-vsctl add-port br0 tap0 | |
199 | ovs-vsctl add-port br0 tap1 \ | |
200 | -- --id=@p get port tap1 \ | |
201 | -- --id=@m create mirror name=m0 select-all=true output-port=@p \ | |
202 | -- set bridge br0 mirrors=@m | |
203 | ||
204 | To later disable mirroring, run: | |
205 | ||
206 | ovs-vsctl clear bridge br0 mirrors | |
207 | ||
208 | Q: How do I configure a VLAN as an RSPAN VLAN, that is, enable | |
209 | mirroring of all traffic to that VLAN? | |
210 | ||
211 | A: The following commands configure br0 with eth0 as a trunk port and | |
212 | tap0 as an access port for VLAN 10. All traffic coming in or going | |
213 | out on tap0, as well as traffic coming in or going out on eth0 in | |
214 | VLAN 10, is also mirrored to VLAN 15 on eth0. The original tag for | |
215 | VLAN 10, in cases where one is present, is dropped as part of | |
216 | mirroring: | |
217 | ||
218 | ovs-vsctl add-br br0 | |
219 | ovs-vsctl add-port br0 eth0 | |
220 | ovs-vsctl add-port br0 tap0 tag=10 | |
221 | ovs-vsctl \ | |
222 | -- --id=@m create mirror name=m0 select-all=true select-vlan=10 \ | |
223 | output-vlan=15 \ | |
224 | -- set bridge br0 mirrors=@m | |
225 | ||
226 | To later disable mirroring, run: | |
227 | ||
228 | ovs-vsctl clear bridge br0 mirrors | |
229 | ||
230 | Mirroring to a VLAN can disrupt a network that contains unmanaged | |
231 | switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a | |
232 | GRE tunnel has fewer caveats than mirroring to a VLAN and should | |
233 | generally be preferred. | |
234 | ||
235 | Q: Can I mirror more than one input VLAN to an RSPAN VLAN? | |
236 | ||
237 | A: Yes, but mirroring to a VLAN strips the original VLAN tag in favor | |
238 | of the specified output-vlan. This loss of information may make | |
239 | the mirrored traffic too hard to interpret. | |
240 | ||
241 | To mirror multiple VLANs, use the commands above, but specify a | |
242 | comma-separated list of VLANs as the value for select-vlan. To | |
243 | mirror every VLAN, use the commands above, but omit select-vlan and | |
244 | its value entirely. | |
245 | ||
246 | When a packet arrives on a VLAN that is used as a mirror output | |
247 | VLAN, the mirror is disregarded. Instead, in standalone mode, OVS | |
248 | floods the packet across all the ports for which the mirror output | |
249 | VLAN is configured. (If an OpenFlow controller is in use, then it | |
250 | can override this behavior through the flow table.) If OVS is used | |
251 | as an intermediate switch, rather than an edge switch, this ensures | |
252 | that the RSPAN traffic is distributed through the network. | |
253 | ||
254 | Mirroring to a VLAN can disrupt a network that contains unmanaged | |
255 | switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a | |
256 | GRE tunnel has fewer caveats than mirroring to a VLAN and should | |
257 | generally be preferred. | |
258 | ||
259 | Q: How do I configure mirroring of all traffic to a GRE tunnel? | |
260 | ||
261 | A: The following commands configure br0 with eth0 and tap0 as trunk | |
262 | ports. All traffic coming in or going out on eth0 or tap0 is also | |
263 | mirrored to gre0, a GRE tunnel to the remote host 192.168.1.10; any | |
264 | traffic arriving on gre0 is dropped: | |
265 | ||
266 | ovs-vsctl add-br br0 | |
267 | ovs-vsctl add-port br0 eth0 | |
268 | ovs-vsctl add-port br0 tap0 | |
269 | ovs-vsctl add-port br0 gre0 \ | |
270 | -- set interface gre0 type=gre options:remote_ip=192.168.1.10 \ | |
271 | -- --id=@p get port gre0 \ | |
272 | -- --id=@m create mirror name=m0 select-all=true output-port=@p \ | |
273 | -- set bridge br0 mirrors=@m | |
274 | ||
275 | To later disable mirroring and destroy the GRE tunnel: | |
276 | ||
277 | ovs-vsctl clear bridge br0 mirrors | |
278 | ovs-vcstl del-port br0 gre0 | |
279 | ||
280 | Q: Does Open vSwitch support ERSPAN? | |
281 | ||
282 | A: No. ERSPAN is an undocumented proprietary protocol. As an | |
283 | alternative, Open vSwitch supports mirroring to a GRE tunnel (see | |
284 | above). | |
285 | ||
286 | ||
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287 | Configuration Problems |
288 | ---------------------- | |
289 | ||
290 | Q: I created a bridge and added my Ethernet port to it, using commands | |
291 | like these: | |
292 | ||
293 | ovs-vsctl add-br br0 | |
294 | ovs-vsctl add-port br0 eth0 | |
295 | ||
296 | and as soon as I ran the "add-port" command I lost all connectivity | |
297 | through eth0. Help! | |
298 | ||
299 | A: A physical Ethernet device that is part of an Open vSwitch bridge | |
300 | should not have an IP address. If one does, then that IP address | |
301 | will not be fully functional. | |
302 | ||
303 | You can restore functionality by moving the IP address to an Open | |
304 | vSwitch "internal" device, such as the network device named after | |
305 | the bridge itself. For example, assuming that eth0's IP address is | |
306 | 192.168.128.5, you could run the commands below to fix up the | |
307 | situation: | |
308 | ||
309 | ifconfig eth0 0.0.0.0 | |
310 | ifconfig br0 192.168.128.5 | |
311 | ||
312 | (If your only connection to the machine running OVS is through the | |
313 | IP address in question, then you would want to run all of these | |
314 | commands on a single command line, or put them into a script.) If | |
315 | there were any additional routes assigned to eth0, then you would | |
316 | also want to use commands to adjust these routes to go through br0. | |
317 | ||
318 | If you use DHCP to obtain an IP address, then you should kill the | |
319 | DHCP client that was listening on the physical Ethernet interface | |
320 | (e.g. eth0) and start one listening on the internal interface | |
321 | (e.g. br0). You might still need to manually clear the IP address | |
322 | from the physical interface (e.g. with "ifconfig eth0 0.0.0.0"). | |
323 | ||
324 | There is no compelling reason why Open vSwitch must work this way. | |
325 | However, this is the way that the Linux kernel bridge module has | |
326 | always worked, so it's a model that those accustomed to Linux | |
327 | bridging are already used to. Also, the model that most people | |
328 | expect is not implementable without kernel changes on all the | |
329 | versions of Linux that Open vSwitch supports. | |
330 | ||
331 | By the way, this issue is not specific to physical Ethernet | |
332 | devices. It applies to all network devices except Open vswitch | |
333 | "internal" devices. | |
334 | ||
335 | Q: I created a bridge and added a couple of Ethernet ports to it, | |
336 | using commands like these: | |
337 | ||
338 | ovs-vsctl add-br br0 | |
339 | ovs-vsctl add-port br0 eth0 | |
340 | ovs-vsctl add-port br0 eth1 | |
341 | ||
342 | and now my network seems to have melted: connectivity is unreliable | |
343 | (even connectivity that doesn't go through Open vSwitch), all the | |
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344 | LEDs on my physical switches are blinking, wireshark shows |
345 | duplicated packets, and CPU usage is very high. | |
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346 | |
347 | A: More than likely, you've looped your network. Probably, eth0 and | |
348 | eth1 are connected to the same physical Ethernet switch. This | |
349 | yields a scenario where OVS receives a broadcast packet on eth0 and | |
350 | sends it out on eth1, then the physical switch connected to eth1 | |
351 | sends the packet back on eth0, and so on forever. More complicated | |
352 | scenarios, involving a loop through multiple switches, are possible | |
353 | too. | |
354 | ||
355 | The solution depends on what you are trying to do: | |
356 | ||
357 | - If you added eth0 and eth1 to get higher bandwidth or higher | |
358 | reliability between OVS and your physical Ethernet switch, | |
359 | use a bond. The following commands create br0 and then add | |
360 | eth0 and eth1 as a bond: | |
361 | ||
362 | ovs-vsctl add-br br0 | |
363 | ovs-vsctl add-bond br0 bond0 eth0 eth1 | |
364 | ||
365 | Bonds have tons of configuration options. Please read the | |
366 | documentation on the Port table in ovs-vswitchd.conf.db(5) | |
367 | for all the details. | |
368 | ||
369 | - Perhaps you don't actually need eth0 and eth1 to be on the | |
370 | same bridge. For example, if you simply want to be able to | |
371 | connect each of them to virtual machines, then you can put | |
372 | each of them on a bridge of its own: | |
373 | ||
374 | ovs-vsctl add-br br0 | |
375 | ovs-vsctl add-port br0 eth0 | |
376 | ||
377 | ovs-vsctl add-br br1 | |
378 | ovs-vsctl add-port br1 eth1 | |
379 | ||
380 | and then connect VMs to br0 and br1. (A potential | |
381 | disadvantage is that traffic cannot directly pass between br0 | |
382 | and br1. Instead, it will go out eth0 and come back in eth1, | |
383 | or vice versa.) | |
384 | ||
385 | - If you have a redundant or complex network topology and you | |
386 | want to prevent loops, turn on spanning tree protocol (STP). | |
387 | The following commands create br0, enable STP, and add eth0 | |
388 | and eth1 to the bridge. The order is important because you | |
389 | don't want have to have a loop in your network even | |
390 | transiently: | |
391 | ||
392 | ovs-vsctl add-br br0 | |
393 | ovs-vsctl set bridge br0 stp_enable=true | |
394 | ovs-vsctl add-port br0 eth0 | |
395 | ovs-vsctl add-port br0 eth1 | |
396 | ||
397 | The Open vSwitch implementation of STP is not well tested. | |
398 | Please report any bugs you observe, but if you'd rather avoid | |
399 | acting as a beta tester then another option might be your | |
400 | best shot. | |
401 | ||
402 | Q: I can't seem to use Open vSwitch in a wireless network. | |
403 | ||
404 | A: Wireless base stations generally only allow packets with the source | |
405 | MAC address of NIC that completed the initial handshake. | |
406 | Therefore, without MAC rewriting, only a single device can | |
407 | communicate over a single wireless link. | |
408 | ||
409 | This isn't specific to Open vSwitch, it's enforced by the access | |
410 | point, so the same problems will show up with the Linux bridge or | |
411 | any other way to do bridging. | |
412 | ||
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413 | Q: Is there any documentation on the database tables and fields? |
414 | ||
415 | A: Yes. ovs-vswitchd.conf.db(5) is a comprehensive reference. | |
416 | ||
c483d489 BP |
417 | |
418 | VLANs | |
419 | ----- | |
420 | ||
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421 | Q: What's a VLAN? |
422 | ||
423 | A: At the simplest level, a VLAN (short for "virtual LAN") is a way to | |
424 | partition a single switch into multiple switches. Suppose, for | |
425 | example, that you have two groups of machines, group A and group B. | |
426 | You want the machines in group A to be able to talk to each other, | |
427 | and you want the machine in group B to be able to talk to each | |
428 | other, but you don't want the machines in group A to be able to | |
429 | talk to the machines in group B. You can do this with two | |
430 | switches, by plugging the machines in group A into one switch and | |
431 | the machines in group B into the other switch. | |
432 | ||
433 | If you only have one switch, then you can use VLANs to do the same | |
434 | thing, by configuring the ports for machines in group A as VLAN | |
435 | "access ports" for one VLAN and the ports for group B as "access | |
436 | ports" for a different VLAN. The switch will only forward packets | |
437 | between ports that are assigned to the same VLAN, so this | |
438 | effectively subdivides your single switch into two independent | |
439 | switches, one for each group of machines. | |
440 | ||
441 | So far we haven't said anything about VLAN headers. With access | |
442 | ports, like we've described so far, no VLAN header is present in | |
443 | the Ethernet frame. This means that the machines (or switches) | |
444 | connected to access ports need not be aware that VLANs are | |
445 | involved, just like in the case where we use two different physical | |
446 | switches. | |
447 | ||
448 | Now suppose that you have a whole bunch of switches in your | |
449 | network, instead of just one, and that some machines in group A are | |
450 | connected directly to both switches 1 and 2. To allow these | |
451 | machines to talk to each other, you could add an access port for | |
452 | group A's VLAN to switch 1 and another to switch 2, and then | |
453 | connect an Ethernet cable between those ports. That works fine, | |
454 | but it doesn't scale well as the number of switches and the number | |
455 | of VLANs increases, because you use up a lot of valuable switch | |
456 | ports just connecting together your VLANs. | |
457 | ||
458 | This is where VLAN headers come in. Instead of using one cable and | |
459 | two ports per VLAN to connect a pair of switches, we configure a | |
460 | port on each switch as a VLAN "trunk port". Packets sent and | |
461 | received on a trunk port carry a VLAN header that says what VLAN | |
462 | the packet belongs to, so that only two ports total are required to | |
463 | connect the switches, regardless of the number of VLANs in use. | |
464 | Normally, only switches (either physical or virtual) are connected | |
465 | to a trunk port, not individual hosts, because individual hosts | |
466 | don't expect to see a VLAN header in the traffic that they receive. | |
467 | ||
468 | None of the above discussion says anything about particular VLAN | |
469 | numbers. This is because VLAN numbers are completely arbitrary. | |
470 | One must only ensure that a given VLAN is numbered consistently | |
471 | throughout a network and that different VLANs are given different | |
472 | numbers. (That said, VLAN 0 is usually synonymous with a packet | |
473 | that has no VLAN header, and VLAN 4095 is reserved.) | |
474 | ||
c483d489 BP |
475 | Q: VLANs don't work. |
476 | ||
477 | A: Many drivers in Linux kernels before version 3.3 had VLAN-related | |
478 | bugs. If you are having problems with VLANs that you suspect to be | |
479 | driver related, then you have several options: | |
480 | ||
481 | - Upgrade to Linux 3.3 or later. | |
482 | ||
483 | - Build and install a fixed version of the particular driver | |
484 | that is causing trouble, if one is available. | |
485 | ||
486 | - Use a NIC whose driver does not have VLAN problems. | |
487 | ||
488 | - Use "VLAN splinters", a feature in Open vSwitch 1.4 and later | |
489 | that works around bugs in kernel drivers. To enable VLAN | |
490 | splinters on interface eth0, use the command: | |
491 | ||
7b287e99 | 492 | ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true |
c483d489 BP |
493 | |
494 | For VLAN splinters to be effective, Open vSwitch must know | |
495 | which VLANs are in use. See the "VLAN splinters" section in | |
496 | the Interface table in ovs-vswitchd.conf.db(5) for details on | |
497 | how Open vSwitch infers in-use VLANs. | |
498 | ||
499 | VLAN splinters increase memory use and reduce performance, so | |
500 | use them only if needed. | |
501 | ||
502 | - Apply the "vlan workaround" patch from the XenServer kernel | |
503 | patch queue, build Open vSwitch against this patched kernel, | |
504 | and then use ovs-vlan-bug-workaround(8) to enable the VLAN | |
505 | workaround for each interface whose driver is buggy. | |
506 | ||
507 | (This is a nontrivial exercise, so this option is included | |
508 | only for completeness.) | |
509 | ||
510 | It is not always easy to tell whether a Linux kernel driver has | |
511 | buggy VLAN support. The ovs-vlan-test(8) and ovs-test(8) utilities | |
512 | can help you test. See their manpages for details. Of the two | |
513 | utilities, ovs-test(8) is newer and more thorough, but | |
514 | ovs-vlan-test(8) may be easier to use. | |
515 | ||
516 | Q: VLANs still don't work. I've tested the driver so I know that it's OK. | |
517 | ||
518 | A: Do you have VLANs enabled on the physical switch that OVS is | |
519 | attached to? Make sure that the port is configured to trunk the | |
520 | VLAN or VLANs that you are using with OVS. | |
521 | ||
522 | Q: Outgoing VLAN-tagged traffic goes through OVS to my physical switch | |
523 | and to its destination host, but OVS seems to drop incoming return | |
524 | traffic. | |
525 | ||
526 | A: It's possible that you have the VLAN configured on your physical | |
527 | switch as the "native" VLAN. In this mode, the switch treats | |
528 | incoming packets either tagged with the native VLAN or untagged as | |
529 | part of the native VLAN. It may also send outgoing packets in the | |
530 | native VLAN without a VLAN tag. | |
531 | ||
532 | If this is the case, you have two choices: | |
533 | ||
534 | - Change the physical switch port configuration to tag packets | |
535 | it forwards to OVS with the native VLAN instead of forwarding | |
536 | them untagged. | |
537 | ||
538 | - Change the OVS configuration for the physical port to a | |
539 | native VLAN mode. For example, the following sets up a | |
540 | bridge with port eth0 in "native-tagged" mode in VLAN 9: | |
541 | ||
542 | ovs-vsctl add-br br0 | |
543 | ovs-vsctl add-port br0 eth0 tag=9 vlan_mode=native-tagged | |
544 | ||
545 | In this situation, "native-untagged" mode will probably work | |
546 | equally well. Refer to the documentation for the Port table | |
547 | in ovs-vswitchd.conf.db(5) for more information. | |
548 | ||
549 | Q: Can I configure an IP address on a VLAN? | |
550 | ||
551 | A: Yes. Use an "internal port" configured as an access port. For | |
552 | example, the following configures IP address 192.168.0.7 on VLAN 9. | |
553 | That is, OVS will forward packets from eth0 to 192.168.0.7 only if | |
554 | they have an 802.1Q header with VLAN 9. Conversely, traffic | |
555 | forwarded from 192.168.0.7 to eth0 will be tagged with an 802.1Q | |
556 | header with VLAN 9: | |
557 | ||
558 | ovs-vsctl add-br br0 | |
559 | ovs-vsctl add-port br0 eth0 | |
560 | ovs-vsctl add-port br0 vlan9 tag=9 -- set interface vlan9 type=internal | |
561 | ifconfig vlan9 192.168.0.7 | |
562 | ||
563 | Q: My OpenFlow controller doesn't see the VLANs that I expect. | |
564 | ||
565 | A: The configuration for VLANs in the Open vSwitch database (e.g. via | |
566 | ovs-vsctl) only affects traffic that goes through Open vSwitch's | |
567 | implementation of the OpenFlow "normal switching" action. By | |
568 | default, when Open vSwitch isn't connected to a controller and | |
569 | nothing has been manually configured in the flow table, all traffic | |
570 | goes through the "normal switching" action. But, if you set up | |
571 | OpenFlow flows on your own, through a controller or using ovs-ofctl | |
572 | or through other means, then you have to implement VLAN handling | |
573 | yourself. | |
574 | ||
575 | You can use "normal switching" as a component of your OpenFlow | |
576 | actions, e.g. by putting "normal" into the lists of actions on | |
577 | ovs-ofctl or by outputting to OFPP_NORMAL from an OpenFlow | |
578 | controller. This will only be suitable for some situations, | |
579 | though. | |
580 | ||
f0a0c1a6 BP |
581 | Q: I configured ports on a bridge as access ports with different VLAN |
582 | tags, like this: | |
583 | ||
584 | ovs-vsctl add-br br0 | |
585 | ovs-vsctl set-controller br0 tcp:192.168.0.10:6633 | |
586 | ovs-vsctl add-port br0 eth0 | |
587 | ovs-vsctl add-port br0 tap0 tag=9 | |
588 | ovs-vsctl add-port br0 tap1 tag=10 | |
589 | ||
590 | but the VMs running behind tap0 and tap1 can still communicate, | |
591 | that is, they are not isolated from each other even though they are | |
592 | on different VLANs. | |
593 | ||
594 | A: Do you have a controller configured on br0 (as the commands above | |
595 | do)? If so, then this is a variant on the previous question, "My | |
596 | OpenFlow controller doesn't see the VLANs that I expect," and you | |
597 | can refer to the answer there for more information. | |
598 | ||
c483d489 BP |
599 | |
600 | Controllers | |
601 | ----------- | |
602 | ||
7b287e99 JP |
603 | Q: What versions of OpenFlow does Open vSwitch support? |
604 | ||
605 | A: Open vSwitch supports OpenFlow 1.0. It also includes a number of | |
606 | extensions that bring many of the features from later versions of | |
607 | OpenFlow. Work is underway to provide support for later versions and | |
608 | can be tracked here: | |
609 | ||
610 | http://openvswitch.org/development/openflow-1-x-plan/ | |
611 | ||
c483d489 BP |
612 | Q: I'm getting "error type 45250 code 0". What's that? |
613 | ||
614 | A: This is a Open vSwitch extension to OpenFlow error codes. Open | |
615 | vSwitch uses this extension when it must report an error to an | |
616 | OpenFlow controller but no standard OpenFlow error code is | |
617 | suitable. | |
618 | ||
619 | Open vSwitch logs the errors that it sends to controllers, so the | |
620 | easiest thing to do is probably to look at the ovs-vswitchd log to | |
621 | find out what the error was. | |
622 | ||
623 | If you want to dissect the extended error message yourself, the | |
624 | format is documented in include/openflow/nicira-ext.h in the Open | |
625 | vSwitch source distribution. The extended error codes are | |
626 | documented in lib/ofp-errors.h. | |
627 | ||
628 | Q1: Some of the traffic that I'd expect my OpenFlow controller to see | |
629 | doesn't actually appear through the OpenFlow connection, even | |
630 | though I know that it's going through. | |
631 | Q2: Some of the OpenFlow flows that my controller sets up don't seem | |
632 | to apply to certain traffic, especially traffic between OVS and | |
633 | the controller itself. | |
634 | ||
635 | A: By default, Open vSwitch assumes that OpenFlow controllers are | |
636 | connected "in-band", that is, that the controllers are actually | |
637 | part of the network that is being controlled. In in-band mode, | |
638 | Open vSwitch sets up special "hidden" flows to make sure that | |
639 | traffic can make it back and forth between OVS and the controllers. | |
640 | These hidden flows are higher priority than any flows that can be | |
641 | set up through OpenFlow, and they are not visible through normal | |
642 | OpenFlow flow table dumps. | |
643 | ||
644 | Usually, the hidden flows are desirable and helpful, but | |
645 | occasionally they can cause unexpected behavior. You can view the | |
646 | full OpenFlow flow table, including hidden flows, on bridge br0 | |
647 | with the command: | |
648 | ||
649 | ovs-appctl bridge/dump-flows br0 | |
650 | ||
651 | to help you debug. The hidden flows are those with priorities | |
652 | greater than 65535 (the maximum priority that can be set with | |
653 | OpenFlow). | |
654 | ||
655 | The DESIGN file at the top level of the Open vSwitch source | |
656 | distribution describes the in-band model in detail. | |
657 | ||
658 | If your controllers are not actually in-band (e.g. they are on | |
659 | localhost via 127.0.0.1, or on a separate network), then you should | |
660 | configure your controllers in "out-of-band" mode. If you have one | |
661 | controller on bridge br0, then you can configure out-of-band mode | |
662 | on it with: | |
663 | ||
664 | ovs-vsctl set controller br0 connection-mode=out-of-band | |
665 | ||
666 | Q: I configured all my controllers for out-of-band control mode but | |
667 | "ovs-appctl bridge/dump-flows" still shows some hidden flows. | |
668 | ||
669 | A: You probably have a remote manager configured (e.g. with "ovs-vsctl | |
670 | set-manager"). By default, Open vSwitch assumes that managers need | |
671 | in-band rules set up on every bridge. You can disable these rules | |
672 | on bridge br0 with: | |
673 | ||
674 | ovs-vsctl set bridge br0 other-config:disable-in-band=true | |
675 | ||
676 | This actually disables in-band control entirely for the bridge, as | |
677 | if all the bridge's controllers were configured for out-of-band | |
678 | control. | |
679 | ||
680 | Q: My OpenFlow controller doesn't see the VLANs that I expect. | |
681 | ||
682 | A: See answer under "VLANs", above. | |
683 | ||
5cb2356b BP |
684 | Q: I ran "ovs-ofctl add-flow br0 nw_dst=192.168.0.1,actions=drop" |
685 | but I got a funny message like this: | |
686 | ||
687 | ofp_util|INFO|normalization changed ofp_match, details: | |
688 | ofp_util|INFO| pre: nw_dst=192.168.0.1 | |
689 | ofp_util|INFO|post: | |
690 | ||
691 | and when I ran "ovs-ofctl dump-flows br0" I saw that my nw_dst | |
692 | match had disappeared, so that the flow ends up matching every | |
693 | packet. | |
694 | ||
695 | A: The term "normalization" in the log message means that a flow | |
696 | cannot match on an L3 field without saying what L3 protocol is in | |
697 | use. The "ovs-ofctl" command above didn't specify an L3 protocol, | |
698 | so the L3 field match was dropped. | |
699 | ||
700 | In this case, the L3 protocol could be IP or ARP. A correct | |
701 | command for each possibility is, respectively: | |
702 | ||
703 | ovs-ofctl add-flow br0 ip,nw_dst=192.168.0.1,actions=drop | |
704 | ||
705 | and | |
706 | ||
707 | ovs-ofctl add-flow br0 arp,nw_dst=192.168.0.1,actions=drop | |
708 | ||
709 | Similarly, a flow cannot match on an L4 field without saying what | |
710 | L4 protocol is in use. For example, the flow match "tp_src=1234" | |
711 | is, by itself, meaningless and will be ignored. Instead, to match | |
712 | TCP source port 1234, write "tcp,tp_src=1234", or to match UDP | |
713 | source port 1234, write "udp,tp_src=1234". | |
714 | ||
c5b25863 BP |
715 | Q: How can I figure out the OpenFlow port number for a given port? |
716 | ||
717 | A: The OFPT_FEATURES_REQUEST message requests an OpenFlow switch to | |
718 | respond with an OFPT_FEATURES_REPLY that, among other information, | |
719 | includes a mapping between OpenFlow port names and numbers. From a | |
720 | command prompt, "ovs-ofctl show br0" makes such a request and | |
721 | prints the response for switch br0. | |
722 | ||
723 | The Interface table in the Open vSwitch database also maps OpenFlow | |
724 | port names to numbers. To print the OpenFlow port number | |
725 | associated with interface eth0, run: | |
726 | ||
727 | ovs-vsctl get Interface eth0 ofport | |
728 | ||
729 | You can print the entire mapping with: | |
730 | ||
731 | ovs-vsctl -- --columns=name,ofport list Interface | |
732 | ||
733 | but the output mixes together interfaces from all bridges in the | |
734 | database, so it may be confusing if more than one bridge exists. | |
735 | ||
736 | In the Open vSwitch database, ofport value -1 means that the | |
737 | interface could not be created due to an error. (The Open vSwitch | |
738 | log should indicate the reason.) ofport value [] (the empty set) | |
739 | means that the interface hasn't been created yet. The latter is | |
740 | normally an intermittent condition (unless ovs-vswitchd is not | |
741 | running). | |
7b287e99 | 742 | |
af1ac4b9 BP |
743 | Q: I added some flows with my controller or with ovs-ofctl, but when I |
744 | run "ovs-dpctl dump-flows" I don't see them. | |
745 | ||
746 | A: ovs-dpctl queries a kernel datapath, not an OpenFlow switch. It | |
747 | won't display the information that you want. You want to use | |
748 | "ovs-ofctl dump-flows" instead. | |
749 | ||
c483d489 BP |
750 | Contact |
751 | ------- | |
752 | ||
753 | bugs@openvswitch.org | |
754 | http://openvswitch.org/ |