Information Technology Reference
In-Depth Information
CRB is enabled with the bridge crb global command. The decision to route or bridge is in the
hands of the transparent bridge group, with the bridge number route ip command, which
configures IP to be routed in a bridge group.
The show interfaces crb command shows information about which protocols are routed and
which are bridged.
IRB
IRB was introduced in IOS 11.2 as an enhancement to CRB. With IRB, a protocol can be routed
between routed interfaces, bridged interfaces, or different bridge groups. As shown in Figure
4-19, this permits routing of IP from routed interfaces to bridged interfaces.
IRB
Figure 4-19
E3: bridge group 1
BRIDGE IP
E2: bridge group 1
E0: 192.168.1.1/24
BVI: 192.168.3.1/24
ROUTE IP
E1: 192.168.2.1/24
IRB is enabled with the bridge irb global configuration command. A virtual IRB interface is
created to have packets from the routed interfaces reach hosts in the bridge interfaces. The
command to create the virtual bridge interface is interface bvi bridge-group .
The router configuration is shown in Example 4-6. In this example, the virtual bridge interface
is created for Bridge group 1 with the interface bvi 1 command. IRB is enabled with the bridge
irb command. With the bridge 1 route ip command, IP is routed between Ethernet 0, Ethernet
1, and the BVI interface; IP is bridged between Ethernet 2 and Ethernet 3.
Configuration of IRB
Example 4-6
bridge 1 protocol ieee
bridge irb
bridge 1 route ip
!
interface ethernet 0
ip address 192.168.1.1 255.255.255.0
!
interface ethernet 1
ip address 192.168.2.1 255.255.255.0
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