Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 400)

Adding a loopback interface
You can configure the device to use a loopback interface instead of a specific port or virtual routing
interface to communicate with a BGP4 neighbor. A loopback interface adds stability to the network by
working around route flap problems that can occur due to unstable links between the device and
neighbors.
Loopback interfaces are always up, regardless of the states of physical interfaces. Loopback
interfaces are especially useful for IBGP neighbors (neighbors in the same AS) that are multiple hops
away from the device. When you configure a BGP4 neighbor on the device, you can specify whether
the device uses the loopback interface to communicate with the neighbor. As long as a path exists
between the device and the neighbor, BGP4 information can be exchanged. The BGP4 session is not
associated with a specific link, but is instead associated with the virtual interfaces.
NOTE
If you configure the Brocade device to use a loopback interface to communicate with a BGP4
neighbor, the peer IP address on the remote device pointing to your loopback address must be
configured.
To add a loopback interface, enter commands such as the following.
device(config-bgp)# exit
device(config)# int loopback 1
device(config-lbif-1)# ip address 10.0.0.1/24
Syntax: [no] interface loopback num
The num value can be from 1 through the maximum number of loopback interfaces supported on the
device.
Adding BGP4 neighbors
Because BGP4 does not contain a peer discovery process, for each BGP4 neighbor (peer), you must
indicate the IP address and the AS number of each neighbor. Neighbors that are in different
autonomous systems communicate using EBGP. Neighbors within the same AS communicate using
IBGP.
NOTE
If the device has multiple neighbors with similar attributes, you can simplify configuration by
configuring a peer group, then adding individual neighbors to it. The configuration steps are similar,
except you specify a peer group name instead of a neighbor IP address when configuring the neighbor
parameters, then add individual neighbors to the peer group.
NOTE
The device attempts to establish a BGP4 session with a neighbor as soon as you enter a command
specifying the IP address of the neighbor. If you want to completely configure the neighbor parameters
before the device establishes a session with the neighbor, you can administratively shut down the
neighbor.
To add a BGP4 neighbor with an IP address 10.157.22.26, enter the following command.
device(config-bgp-router)# neighbor 10.157.22.26 remote-as 100
The neighbor ip-addr must be a valid IP address.
Adding a loopback interface
400 FastIron Ethernet Switch Layer 3 Routing Configuration Guide
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