[ovs-discuss] Open vSwitch with tap interface

Thu Jul 19 00:48:21 UTC 2012

Hi OVS experts,

I am new to OVS and trying to replace Linux bridge (brctl) utility with OVS.

Using Linux  bridge, I have two VM's based on QEMU/KVM using two tap interfaces tap0.mxu and tap1.mxu and they are connected thru my bridge mxu-br0:

brctl show mxu-br0
bridge name     bridge id               STP enabled          interfaces
mxu-br0         8000.6a403c9462ff       no                   tap0.mxu
                                                                                          tap1.mxu

My two VM's, mxu-br0,  tap0.mxu and tap1.mxu are all on the same Liunx machine and you can see them all up so I can send ping btw my two VM's without any problem.

>ifconfig | more
eth0      Link encap:Ethernet  HWaddr 30:e4:db:c2:a1:a4
          inet addr:172.19.124.54  Bcast:172.19.124.255  Mask:255.255.255.0
          inet6 addr: fe80::32e4:dbff:fec2:a1a4/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:15000589 errors:0 dropped:870 overruns:0 frame:0
          TX packets:7831073 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:15172609160 (15.1 GB)  TX bytes:2499636852 (2.4 GB)
          Memory:b3160000-b3180000

eth1      Link encap:Ethernet  HWaddr 30:e4:db:c2:a1:a5
          inet addr:21.255.255.253  Bcast:21.255.255.255  Mask:255.0.0.0
          inet6 addr: fe80::32e4:dbff:fec2:a1a5/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2611 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:241898 (241.8 KB)
          Memory:b3120000-b3140000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:10098544920 errors:0 dropped:0 overruns:0 frame:0
          TX packets:10098544920 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:811112857751 (811.1 GB)  TX bytes:811112857751 (811.1 GB)

mxu-br0   Link encap:Ethernet  HWaddr 6a:40:3c:94:62:ff
          inet6 addr: fe80::6840:3cff:fe94:62ff/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:20 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:4101 (4.1 KB)

tap0.mxu  Link encap:Ethernet  HWaddr 6a:40:3c:94:62:ff
          inet6 addr: fe80::6840:3cff:fe94:62ff/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:19 errors:0 dropped:0 overruns:0 frame:0
          TX packets:47 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:2742 (2.7 KB)  TX bytes:8854 (8.8 KB)

tap1.mxu  Link encap:Ethernet  HWaddr ee:0d:fe:17:53:5d
          inet6 addr: fe80::ec0d:feff:fe17:535d/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:21 errors:0 dropped:0 overruns:0 frame:0
          TX packets:24 errors:0 dropped:1 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:2598 (2.5 KB)  TX bytes:4450 (4.4 KB)

Now I use OVS to create bridge mxu-ovs-br1:

>ovs-vsctl show
92076a61-e1bc-4610-997e-22cc173891ab
    Bridge "mxu-ovs-br1"
        Port "mxu-ovs-br1"
            Interface "mxu-ovs-br1"
                type: internal
        Port "tap1.mxu"
            Interface "tap1.mxu"
        Port "tap0.mxu"
            Interface "tap0.mxu"

I see tap0.mxu and tap1.mxu are up but not bridge mxu-ovs-br1 and it seems that I could not use ifconfig to bring up mxu-ovs-br1
(not the same as the Linux bridge utility).  With OVS as my soft switch, my two VMs (still the same, identical QEMU/KVM based ) could not ping each other.

Does anybody know whether this is because OVS does not work with tap interface (created using tunctl utility) or I did not configure everything correctly?
My OVS is built from  openvswitch-1.6.1.

> ifconfig | more
eth0      Link encap:Ethernet  HWaddr 58:8d:09:08:9a:04
          inet addr:172.28.12.88  Bcast:172.28.12.255  Mask:255.255.255.0
          inet6 addr: fe80::5a8d:9ff:fe08:9a04/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3512603 errors:0 dropped:1265 overruns:0 frame:0
          TX packets:6108402 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:567115246 (567.1 MB)  TX bytes:9147031239 (9.1 GB)
          Memory:b1960000-b1980000

tap0.mxu  Link encap:Ethernet  HWaddr 4a:ad:a0:91:81:f9
          inet6 addr: fe80::48ad:a0ff:fe91:81f9/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:402 errors:0 dropped:0 overruns:0 frame:0
          TX packets:62 errors:0 dropped:1 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:81538 (81.5 KB)  TX bytes:10343 (10.3 KB)

tap1.mxu  Link encap:Ethernet  HWaddr ee:dc:21:63:c0:79
          inet6 addr: fe80::ecdc:21ff:fe63:c079/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:401 errors:0 dropped:0 overruns:0 frame:0
          TX packets:37 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:80879 (80.8 KB)  TX bytes:5762 (5.7 KB)

Thanks in advance,

Milton
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