What does it mean Bridg-groups on interface?

Unanswered Question
Jun 22nd, 2010

Dear All,

Can you let me know what does it mean "Bridge-groups1" on interface as below:

interface GigabitEthernet0/0
no ip address
duplex auto
speed auto
bridge-group 1
interface GigabitEthernet0/1
no ip address
duplex auto
speed auto
bridge-group 1


interface BVI1
ip address

the interface gi0/0 and Gi0/1 is active/active right?

Best Regards,


I have this problem too.
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Tharak Abraham Tue, 06/22/2010 - 23:11


This is part of IRB or Integrated Routing and Bridging.

With this you can Route and Bridge on the same interfaces.

The Bridge group 1 on the gig interfaces tells the router to be part of that group and the BVI1 infact represents the Bridge Group 1 to the rest of the network.(for routing)

Yes,  both the Gig interfaces should be active.

You may specify the protocol which you want to be routed too, say "bridge 1 route ip"

and for running spanning tree you need "bridge 1 protocol ieee"

rechard_hk Wed, 06/23/2010 - 01:16

Dear Tharak,

Thaks you for your reply!!!

i have some question to ask you about bridg-groups conect to Cat.3560 (2 unit). Let me detail you that:

I have cisco Router 2821 with 3 interface and Cat.3560 (2unit). i would like to connect from Cisco Router 2821 f0/0 connect to internet and f0/1,f0/2 connect to both switch ( Cat.3560) then both cat.3560 connect to access switch.

So i mean that from cisco 2821 to cat.3560 (both) i use protocol bridge-groups1 and from cat.3560 (both) connect to access .

is it possible on this ?

Note : my point i would like to do load balancing ( Active/Active)

Best Regards,


Tharak Abraham Wed, 06/23/2010 - 04:37

Hi Rechard,

Yes, it should work as per your design.

You want the BVI to be the gateway for the hosts connected to both the Cats ?

By load balancing, i hope you are just segregating your Users on two different switches, if i got you right ?

patrickvanham Wed, 06/23/2010 - 07:21

BVI will participate in spanning-tree, meaning one of the physical interfaces attached should go into blocking.The interface will be up/up but only one of the two will forward traffic. If you disable spanning tree you'll only get a layer 2 loop and likely both routers will go down due to broadcast storms.

If you require load-sharing a portchannel would suit your purpose better, but you cannot channel with one interaface to two separate 3560 switches.


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