April 1, 2015

Debian Linux Bridge Mode not forwarding

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Hello All

I am trying to bridge lan adaptor eth0 with the eth1 interface exposed by sierra wireless lte modem.

When i create a bridge using the following commands
brctl addbr br0
brctl addif br0 eth0 eth1
then i bring up the br0 interface

brctl show shows that bridge is up and running and ports are set to forwarding mode

br0
bridge id 8000.e0699577868f
designated root 8000.e0699577868f
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 0.64 tcn timer 0.00
topology change timer 0.00 gc timer 15.64
flags

eth0 (1)
port id 8001 state forwarding
designated root 8000.e0699577868f path cost 4
designated bridge 8000.e0699577868f message age timer 0.00
designated port 8001 forward delay timer 0.00
designated cost 0 hold timer 0.00
flags

eth1 (2)
port id 8002 state forwarding
designated root 8000.e0699577868f path cost 100
designated bridge 8000.e0699577868f message age timer 0.00
designated port 8002 forward delay timer 0.00
designated cost 0 hold timer 0.00
flags

However as soon as first packet is sent via the bridge to eth1, i see that the forwarding status of eth1 changes automatically to disabled.

br0
bridge id 8000.e0699577868f
designated root 8000.e0699577868f
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 0.64 tcn timer 0.00
topology change timer 0.00 gc timer 15.64
flags

eth0 (1)
port id 8001 state forwarding
designated root 8000.e0699577868f path cost 4
designated bridge 8000.e0699577868f message age timer 0.00
designated port 8001 forward delay timer 0.00
designated cost 0 hold timer 0.00
flags

eth1 (2)
port id 8002 state disabled
designated root 8000.e0699577868f path cost 100
designated bridge 8000.e0699577868f message age timer 0.00
designated port 8002 forward delay timer 0.00
designated cost 0 hold timer 0.00
flags

Kindly let me know how to debug this issue and if we can use logging to identify the problem?

Click Here!