Cisco virtual bridge interfaces

Use a Bridge Virtual Interface when you want to have multiple router interfaces act as members of a single Ethernet collision domain, or bridge two separate network segments together.  Lots of wireless bridges use this function to attach their wireless clients to a local Ethernet.  Start by defining the bridge group:

router(config)#bridge 202 protocol ieee
router(config)#bridge 202 route ip

Then put some interfaces into that group:

router(config)#int faste31
router(config-if)#bridge-group 202
router(config-if)#int faste32
router(config-if)#bridge-group 202
router(config-if)#int faste33

Then, create the BVI interface:

router(config-if)#int bvi202
router(config-if)#desc new server cluster
router(config-if)#ip addr 198.22.62.65 255.255.255.240

Your BVI interface should be up, and all these formerly “router” ports should now be a transparent bridge.

(Why am I using BVI instead of VLAN on a bunch of Ethernet ports?  This particular switch is configured as a router, and it really wants to treat all the interfaces as router interfaces.  It insists it doesn’t know how to configure a VLAN.  I’m certain that Cisco has a reason for this, but their explanation might put me off my feed.)