这是一个IRB的配置实例。这个配置允许在两个以太口之间桥接IP，路由IP则使用一个桥接虚拟接口（BVI）。在下面的网络图中，当PCA试图连络PCB时，路由器R1检查到目标IP地址（PCB）是在同一网段，于是数据包被路由器R1从E0桥接到E1,而数据包是由BVI进行路由的。这样，IP协议在路由器既桥接又路由了。

Current configuration:
!
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname R1
!
!
ip subnet-zero
no ip domain-lookup
bridge irb
!– This command enables the IRB feature on this router.
!
!
!
interface Ethernet0
no ip address
no ip directed-broadcast
bridge-group 1
!– The interface E0 is in bridge-group 1.
!
Interface Ethernet1
no ip address
no ip directed-broadcast
bridge-group 1
!– The interface E1 is in bridge-group 1.
!
Interface Serial0
ip address 10.10.20.1 255.255.255.0
no ip directed-broadcast
no ip mroute-cache
no fair-queue
!
interface Serial1
no ip address
no ip directed-broadcast
shutdown
!
interface BVI1
ip address 10.10.10.1 255.255.255.0
!– An ip address is assigned to the logical BVI for routing
!– IP between bridged interfaces and routed interfaces.
no ip directed-broadcast
!
ip classless
ip route 10.10.30.0 255.255.255.0 10.10.20.2
!
bridge 1 protocol ieee
!– This command enables the bridging on this router.
bridge 1 route ip
!– This command enable bridging as well routing for IP protocol.
!
line con 0
transport input none
line aux 0
line vty 0 4
!
end

show Command Outputs
show interfaces [interface] irb
This command displays the protocols that can be routed or bridged for the specified interface, as follows:
R1#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

R1#

Cisco路由器提供集成的路由与桥接（Integrated Routing and Bridging，IRB）功能。当配置了IRB后，不可路由的协议数据流可以在配置为相同网桥组的端口上实现桥接交换，同时可以路由的协议数据流则在其他的路由端口或不同的网桥组之间实现路由。
 

这里提到了一个概念，即网桥组（Bridge-Group）。要实现不同的端口之间的桥接交换，必须将这些端口归到同一个网桥组当中。从概念上说，配置为同一个网桥组中