Bridge Group Virtual Interface - BVI

Cisco Bridge-group Virtual Interface (BVI)

A BVI (Bridge Group Virtual Interface) is a routed interface that represents a set of Ethernet interfaces that gets bridged. By using  a Bridge group Virtual Interface, you can convert  multiple Router Ethernet WAN interfaces as members of a common Ethernet broadcast domain 

This configuration allows bridging IP between two Ethernet interfaces, and routing IP from bridgedinterfaces using a Bridge Virtual Interface (BVI). By using Integrated Routing and Bridging (IRB)technique, a Cisco router  can be turned into a L3 switch. Ip addresses can be assigned on Bridge-Group Virtual Interfaces (BVIs), similar to VLAN interfaces as in L3 switches. A BVI is a virtual routed interface that has all network layer attributes, eg: a network address can be assigned to it and does not support bridging.

Bridge groups are defined by a unique number and are used for router bridging configuration. Network traffic is bridged between all interfaces that belong to the same bridge group.

Step by Step Bridge Group Virtual Interface (BVI) Configuration

Integrated Routing and Bridging configuration on Router1:

Router (config)#int fa0/0

Router (config-if)#bridge-group 1

Router (config-if)#no shut

Router(config-if)#exit

Router (config)#

Router (config-if)#int fa1/0

Router(config-if)#bridge-group 1

Router (config-if)#no shut

Router(config-if)#exit

Router(config)#

Create Bridge Group Virtual Interface (BVI) and configure the IP and Routing credentials.

Router1(config)#bridge irb

Router (config)#int bvi1

Router(config-if)#ip add 192.168.2.1 255.255.255.0

Router(config-if)#exit

Router(config)#bridge 1 protocol ieee

Router (config)#bridge 1 route ip

Router(config)#

Note: The bridge 1 protocol ieee global configuration command removes bridge-group 1 spanning-disabled interface subcommand on Fa0/0 and Fa1/0 and hence enables STP on bridged interfaces.

Find Bridge Group Virtual Interface (BVI) show command outputs

Router#sh spanning-tree brief

Bridge group 1

Spanning tree enabled protocol ieee

Root ID    Priority    32768

Address     cc01.01e0.0000

This bridge is the root

Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

Bridge ID  Priority    32768

Address     cc01.01e0.0000

Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

Aging Time 300

Interface                                   Designated

Name                 Port ID Prio Cost  Sts Cost  Bridge ID            Port ID

——————– ——- —- —– — —– ——————– —–

FastEthernet0/0      128.2    128    19 FWD     0 32768 cc01.01e0.0000 128.2

FastEthernet1/0      128.3    128    19 FWD     0 32768 cc01.01e0.0000 128.3

Router#sh bridge group

Bridge Group 1 is running the IEEE compatible Spanning Tree protocol

Port 2 (FastEthernet0/0) of bridge group 1 is forwarding

Port 3 (FastEthernet1/0) of bridge group 1 is forwarding

show interfaces [interface] irb

This command displays the protocols that can be routed or bridged for the specified interface, as follows:

Router#show interface e0 irb

Ethernet0

Routed protocols on Ethernet0:

ip

Bridged protocols on Ethernet0:

ip         ipx

IP protocol is routed as well as bridged.

Software MAC address filter on Ethernet0

Hash Len    Address      Matches  Act      Type

0×00:  0 ffff.ffff.ffff     0     RCV  Physical broadcast

0x2A:  0 0900.2b01.0001     0     RCV  DEC spanning tree

0x9E:  0 0000.0c3a.5092     0     RCV  Interface MAC address

0x9E:  1 0000.0c3a.5092     0     RCV  Bridge-group Virtual Interface

0xC0:  0 0100.0ccc.cccc    157    RCV  CDP

0xC2:  0 0180.c200.0000     0     RCV  IEEE spanning tree

0xC2:  1 0180.c200.0000     0     RCV  IBM spanning tree