Bridge mode configuration

Unanswered Question
Jun 18th, 2008
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Bridge mode configuration in router


The Two routers connected through leased line for WAN link.

The router A and B not communicating after the following configuration.

Please let us know any configuration issue



Router A

int fa0/1

no ip address

duplex auto

bridge-group 64


int bvi64

ip address 192.168.2.2 255.255.255.0


int serial0

ip address 172.26.8.1 255.255.255.0


ip route 0.0.0.0 0.0.0.0 192.168.2.1


bridge 64 protocol ieee

bridge 64 route ip


Router B


int fa0/1

no ip address

duplex auto

bridge-group 64


int bvi64

ip address 192.168.2.1 255.255.255.0


int serial0

ip address 172.26.8.2 255.255.255.0


ip route 0.0.0.0 0.0.0.0 192.168.2.2


bridge 64 protocol ieee

bridge 64 route ip


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aravindhs Thu, 06/19/2008 - 01:23
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Hi,


you have not enabled the serial wan interfaces with bridging.


You must have all these commands on both your routers -

Govindan#sh run | inc bvi|bridge

bridge irb

bridge-group 5

bridge-group 5

bridge 5 protocol ieee

bridge 5 route ip


Your serial interfaces dont need to have an ip address.


But ..


config t

bridge 5 protocol ieee

bridge 5 route ip

int f0/1

bridge-group 5

int bvi 1

ip addr 10.1.1.1 255.255.255.0


similarly on the other router -


config t

bridge 5 protocol ieee

bridge 5 route ip

int f0/1

bridge-group 5

int bvi 1

ip addr 10.1.1.2 255.255.255.0


It should work ..


Let us know how it helped ..


cheers

arav



ntmanjunath Thu, 06/19/2008 - 02:12
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Thanks for the replay.


We have two routers A and B these are connected through WAN Link

Without serial IP these routers will communicate each other after configuring Bridge mode ?


hennigan Thu, 06/19/2008 - 07:50
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The problem is that the same IP subnet exists on both routers' ethernet interfaces, 172.26.8.x/24. Hence, traffic arriving on either router for destinations within that subnet will be treated as local and not be routed over the serial link.


To fix this, make the serial links part of the bridge group. Traffic will then be bridged across all interfaces in the bridge group including the serial links.


One caution, broadcast traffic will also be bridged. This can reduce throughput on the serial link if the FastEthernet networks are chatty. 1% broascast traffic on a FastEthernet is 2/3 of a T1.


Try this config, note that the static routes have been removed. If you want traffic from 172.26.8.x/24 to have a default, put a static on the appropriate router (either A or B) pointing to the egress router, assuming it's on the ethernet subnet. If egress is on another interface, then you'll need to add a default on the remote router pointing to the BVI IP of the egress router.




Router A

int fa0/1

no ip address

duplex auto

bridge-group 64


int bvi64

ip address 192.168.2.2 255.255.255.0


int serial0

no ip address

bridge-group 64


bridge 64 protocol ieee

bridge 64 route ip


Router B


int fa0/1

no ip address

duplex auto

bridge-group 64


int bvi64

ip address 192.168.2.1 255.255.255.0


int serial0

no ip address

bridge-group 64


bridge 64 protocol ieee

bridge 64 route ip




Paolo Bevilacqua Thu, 06/19/2008 - 09:18
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Hi,


reason why you're bridging? As you can notice, bridge usually brings problems an no advantages. With a regular routing setup you would be up and running already.

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