Cisco 1720 WIC-T1 to Ethernet Bridge

[robharbin]

I have a 1720 with a WIC (T1) Serial0 interface and a FastEthernet0 Interface currently performing NAT and routing several public IP's to internal servers.

I need to know how to properly setup a full bridge between the ISP (T1) and the Ethernet interface. I am putting a different router/firewall behind the Cisco and would like the new router to see the WAN gateway and IP block as if it were directly connected.

Any help would be much apprecitated.

[Richard Burts]

If you want to route on the serial interface and you want to bridge on the FastEthernet interface, then you will need to implement Integrated Routing and Bridging (IRB).

You will use a normal configuration of the serial interface. You will need to remove the IP address from the FastEthernet interface. You will need to configure a bridge group and assign the bridge group to the FastEthernet interface. You will need to configure a BVI (Bridged Virtual Interface). You will associate the BVI with the bridge group on the FastEthernet and will assign the IP address that was on the FastEthernet to the BVI. The BVI provides the linkage between the bridged environment and the routed environment.

HTH

Rick

[robharbin]

Sounds like exactly what I need. Do you have any example code for a configuratino like this?

Thanks

[Richard Burts]

It has been a while since I configured IRB and I do not have any sample code where I can put my hands on it. But here are some links which should get you started:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fibm_c/bcfpart1/bcftb.htm#wp1003018

is a link to a discussion of how to configure.

and

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fibm_c/bcfpart1/bcftb.htm#wp1041949

is a link to an example configuration.

HTH

Rick