https://serverfault.com/questions/540831/tap-interfaces-always-disabled-in-linux-bridge

tap interfaces always disabled in linux bridge

I have a physical interface eth0, and I want to create two virtual interfaces and bridge them with eth0. For this purpose I do:

#Create the virtual interfaces tunctl -t tap0 tunctl -t tap1 ifconfig tap0 up ifconfig tap1 up #Create the bridge brctl addbr br0 brctl stp br0 off brctl addif br0 eth0 brctl addif br0 tap0 brctl addif br0 tap1 #Turning up the bridge ifconfig br0 up

However my problem if that the tap interfaces always appear disabled in the bridge, and no traffic flows to them.

$brctl show br0 bridge name bridge id STP enabled interfaces br0 8000.080027cabeba no eth2 tap0 tap1 $brctl showstp br0 br0 bridge id 8000.080027cabeba designated root 8000.080027cabeba root port 0 path cost 0 max age 20.00 bridge max age 20.00 hello time 2.00 bridge hello time 2.00 forward delay 15.00 bridge forward delay 15.00 ageing time 300.01 hello timer 0.00 tcn timer 0.00 topology change timer 0.00 gc timer 298.42 flags eth2 (1) port id 8001 state forwarding designated root 8000.080027cabeba path cost 4 designated bridge 8000.080027cabeba message age timer 0.00 designated port 8001 forward delay timer 12.97 designated cost 0 hold timer 1.24 flags tap0 (2) port id 8002 state disabled designated root 8000.080027cabeba path cost 100 designated bridge 8000.080027cabeba message age timer 0.00 designated port 8002 forward delay timer 0.00 designated cost 0 hold timer 0.00 flags tap1 (3) port id 8003 state disabled designated root 8000.080027cabeba path cost 100 designated bridge 8000.080027cabeba message age timer 0.00 designated port 8003 forward delay timer 0.00 designated cost 0 hold timer 0.00 flags

Is there any way to set the tap interfaces in forwarding state? I do not understand why they are not because STP is disabled.

Cheers

Daniel

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Answer

Carrier (IFF_RUNNING) is only set on a tap when a user has the device handle open.

For a persistent tap created with tunctl, you need an application which attaches to the tap, eg:

http://backreference.org/2010/03/26/tuntap-interface-tutorial/ or

        http://blog.csdn.net/ztguang/article/details/72890346