X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=FAQ;h=75eab993a5c58853bb3d0654cb4b641e01c359a6;hb=refs%2Fheads%2Fmanual;hp=4658bb98b59f583fbf95a369bf30ebe1b1899ccc;hpb=1448105187550e12fe806aa4863ffa5dc397afb8;p=openvswitch diff --git a/FAQ b/FAQ index 4658bb98..75eab993 100644 --- a/FAQ +++ b/FAQ @@ -168,6 +168,137 @@ A: Tunnel and patch virtual ports are not supported, as described in the may not be transmitted. +Terminology +----------- + +Q: I thought Open vSwitch was a virtual Ethernet switch, but the + documentation keeps talking about bridges. What's a bridge? + +A: In networking, the terms "bridge" and "switch" are synonyms. Open + vSwitch implements an Ethernet switch, which means that it is also + an Ethernet bridge. + +Q: What's a VLAN? + +A: See the "VLAN" section below. + + +Basic Configuration +------------------- + +Q: How do I configure a port as an access port? + +A: Add "tag=VLAN" to your "ovs-vsctl add-port" command. For example, + the following commands configure br0 with eth0 as a trunk port (the + default) and tap0 as an access port for VLAN 9: + + ovs-vsctl add-br br0 + ovs-vsctl add-port br0 eth0 + ovs-vsctl add-port br0 tap0 tag=9 + + If you want to configure an already added port as an access port, + use "ovs-vsctl set", e.g.: + + ovs-vsctl set port tap0 tag=9 + +Q: How do I configure a port as a SPAN port, that is, enable mirroring + of all traffic to that port? + +A: The following commands configure br0 with eth0 and tap0 as trunk + ports. All traffic coming in or going out on eth0 or tap0 is also + mirrored to tap1; any traffic arriving on tap1 is dropped: + + ovs-vsctl add-br br0 + ovs-vsctl add-port br0 eth0 + ovs-vsctl add-port br0 tap0 + ovs-vsctl add-port br0 tap1 \ + -- --id=@p get port tap1 \ + -- --id=@m create mirror name=m0 select-all=true output-port=@p \ + -- set bridge br0 mirrors=@m + + To later disable mirroring, run: + + ovs-vsctl clear bridge br0 mirrors + +Q: How do I configure a VLAN as an RSPAN VLAN, that is, enable + mirroring of all traffic to that VLAN? + +A: The following commands configure br0 with eth0 as a trunk port and + tap0 as an access port for VLAN 10. All traffic coming in or going + out on tap0, as well as traffic coming in or going out on eth0 in + VLAN 10, is also mirrored to VLAN 15 on eth0. The original tag for + VLAN 10, in cases where one is present, is dropped as part of + mirroring: + + ovs-vsctl add-br br0 + ovs-vsctl add-port br0 eth0 + ovs-vsctl add-port br0 tap0 tag=10 + ovs-vsctl \ + -- --id=@m create mirror name=m0 select-all=true select-vlan=10 \ + output-vlan=15 \ + -- set bridge br0 mirrors=@m + + To later disable mirroring, run: + + ovs-vsctl clear bridge br0 mirrors + + Mirroring to a VLAN can disrupt a network that contains unmanaged + switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a + GRE tunnel has fewer caveats than mirroring to a VLAN and should + generally be preferred. + +Q: Can I mirror more than one input VLAN to an RSPAN VLAN? + +A: Yes, but mirroring to a VLAN strips the original VLAN tag in favor + of the specified output-vlan. This loss of information may make + the mirrored traffic too hard to interpret. + + To mirror multiple VLANs, use the commands above, but specify a + comma-separated list of VLANs as the value for select-vlan. To + mirror every VLAN, use the commands above, but omit select-vlan and + its value entirely. + + When a packet arrives on a VLAN that is used as a mirror output + VLAN, the mirror is disregarded. Instead, in standalone mode, OVS + floods the packet across all the ports for which the mirror output + VLAN is configured. (If an OpenFlow controller is in use, then it + can override this behavior through the flow table.) If OVS is used + as an intermediate switch, rather than an edge switch, this ensures + that the RSPAN traffic is distributed through the network. + + Mirroring to a VLAN can disrupt a network that contains unmanaged + switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a + GRE tunnel has fewer caveats than mirroring to a VLAN and should + generally be preferred. + +Q: How do I configure mirroring of all traffic to a GRE tunnel? + +A: The following commands configure br0 with eth0 and tap0 as trunk + ports. All traffic coming in or going out on eth0 or tap0 is also + mirrored to gre0, a GRE tunnel to the remote host 192.168.1.10; any + traffic arriving on gre0 is dropped: + + ovs-vsctl add-br br0 + ovs-vsctl add-port br0 eth0 + ovs-vsctl add-port br0 tap0 + ovs-vsctl add-port br0 gre0 \ + -- set interface gre0 type=gre options:remote_ip=192.168.1.10 \ + -- --id=@p get port gre0 \ + -- --id=@m create mirror name=m0 select-all=true output-port=@p \ + -- set bridge br0 mirrors=@m + + To later disable mirroring and destroy the GRE tunnel: + + ovs-vsctl clear bridge br0 mirrors + ovs-vcstl del-port br0 gre0 + +Q: Does Open vSwitch support ERSPAN? + +A: No. ERSPAN is an undocumented proprietary protocol. As an + alternative, Open vSwitch supports mirroring to a GRE tunnel (see + above). + + Configuration Problems ---------------------- @@ -298,6 +429,14 @@ Q: Is there any documentation on the database tables and fields? A: Yes. ovs-vswitchd.conf.db(5) is a comprehensive reference. +Q: When I run ovs-dpctl I no longer see the bridges I created. Instead, + I only see a datapath called "ovs-system". How can I see datapath + information about a particular bridge? + +A: In version 1.9.0, OVS switched to using a single datapath that is + shared by all bridges of that type. The "ovs-appctl dpif/*" + commands provide similar functionality that is scoped by the bridge. + VLANs ----- @@ -624,6 +763,34 @@ A: The OFPT_FEATURES_REQUEST message requests an OpenFlow switch to normally an intermittent condition (unless ovs-vswitchd is not running). +Q: I added some flows with my controller or with ovs-ofctl, but when I + run "ovs-dpctl dump-flows" I don't see them. + +A: ovs-dpctl queries a kernel datapath, not an OpenFlow switch. It + won't display the information that you want. You want to use + "ovs-ofctl dump-flows" instead. + +Q: It looks like each of the interfaces in my bonded port shows up + as an individual OpenFlow port. Is that right? + +A: Yes, Open vSwitch makes individual bond interfaces visible as + OpenFlow ports, rather than the bond as a whole. The interfaces + are treated together as a bond for only a few purposes: + + - Sending a packet to the OFPP_NORMAL port. (When an OpenFlow + controller is not configured, this happens implicitly to + every packet.) + + - The "autopath" Nicira extension action. However, "autopath" + is deprecated and scheduled for removal in February 2013. + + - Mirrors configured for output to a bonded port. + + It would make a lot of sense for Open vSwitch to present a bond as + a single OpenFlow port. If you want to contribute an + implementation of such a feature, please bring it up on the Open + vSwitch development mailing list at dev@openvswitch.org. + Contact -------