Cisco 15327 - Manual (Page 104)

6-8
Ethernet Card Software Feature and Configuration Guide, R7.2
Chapter 6 Configuring Bridges
Bridge IRB Mode
Example 6-8 shows ML-Series card interfaces configured with IP addresses and multiple bridge groups.
Example 6-8 IP Addresses and Multiple Bridge Group
bridge crb
bridge 1 proto rstp
bridge 1 route ip
bridge 2 proto rstp
int f0
ip address 10.10.10.2 255.255.255.0
bridge-group 1
int pos 0
ip address 20.20.20.2 255.255.255.0
bridge-group 1
int f1
bridge-group 2
int pos 1
bridge-group 2
Tip When troubleshooting a bridge crb configuration, make sure the interfaces are not assigned IP addresses
belonging to the same subnet. Routing requires IP addresses to be in different subnets.
Bridge IRB Mode
The integrated routing and bridging mode is enabled with the global command bridge irb. Enabling
bridge irb disables the other modes.
Bridge irb mode is a super-set of the bridge crb mode. Only IRB mode supports a bridged virtual
interface (BVI), which is a virtual Layer 3 interface belonging to a specific bridge-group. A BVI requires
an IP address to function and is visible to all member interfaces of that bridge-group. The only proper
way to route into and out of a bridge-group is with a BVI.
Bridge irb behaves like bridge crb with the following additions:
• If a BVI interface is configured for a bridge-group, the BVI IP address should be the only one
configured on any member of that bridge-group (
Example 6-9 ).
• If both an IP address and a bridge-group are configured on a single interface, enable either IP
bridging or IP routing, but not both (
Example 6-10 ).
• If IP routing is disabled in a bridge-group, all packets will be bridged, and BVI interfaces will not
route IP. This is the default for each bridge-group.
• If IP bridging and IP routing are both enabled in a bridge-group with a BVI, then IP packets can be
bridged between bridge-group members (bridging within the same subnet), and they can be routed
in and out of the bridge-group via the BVI.
• If IP bridging is disabled, but IP routing is enabled in a bridge-group, IP packets can be routed in
and out of the bridge-group through the BVI but cannot be bridged between the Layer 2 interfaces.
The global command bridge x route ip in combination with the global command no bridge x
bridge ip disables IP bridging while enabling IP routing.
Example 6-9 shows ML-Series card interfaces configured in a bridge group and the BVI configured with
an IP address. Both bridging and routing are enabled.