Foundry Configuration Guide for the FESX, FSX, and FWSX
21 - 12
© Foundry Networks, Inc.
December 2005
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 router.
When you configure a BGP4 neighbor on the router, you can specify whether the router uses the loopback
interface to communicate with the neighbor. As long as a path exists between the router and its neighbor, BGP4
information can be exchanged. The BGP4 session is not associated with a specific link but instead is associated
with the virtual interfaces.
You can add up to 24 IP addresses to each loopback interface.
NOTE:
If you configure the Foundry Layer 3 Switch to use a loopback interface to communicate with a BGP4
neighbor, the peer IP address on the remote router pointing to your loopback address must be configured.
To add a loopback interface, enter commands such as those shown in the following example:
FESX424 Router(config-bgp-router)# exit
FESX424 Router(config)# int loopback 1
FESX424 Router(config-lbif-1)# ip address 10.0.0.1/24
Syntax:
interface loopback <num>
The <num> value can be from 1 – 8 on Chassis Layer 3 Switches and the TurboIron/8 Layer 3 Switch. The value
can be from 1 – 4 on the NetIron Stackable Layer 3 Switch.
Adding BGP4 Neighbors
The BGP4 protocol does not contain a peer discovery process. Therefore, for each of the router’s BGP4
neighbors (peers), you must indicate the neighbor’s IP address and the AS each neighbor is in. Neighbors that
are in different ASs communicate using EBGP. Neighbors within the same AS communicate using IBGP.
NOTE:
If the Layer 3 Switch 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. See “Adding a BGP4 Peer Group” on page 21-17.
NOTE:
The Layer 3 Switch attempts to establish a BGP4 session with a neighbor as soon as you enter a
command specifying the neighbor’s IP address. If you want to completely configure the neighbor parameters
before the Layer 3 Switch establishes a session with the neighbor, you can administratively shut down the
neighbor. See “Administratively Shutting Down a Session with a BGP4 Neighbor” on page 21-20.
To add a BGP4 neighbor with IP address 209.157.22.26, enter the following command:
FESX424 Router(config-bgp-router)# neighbor 209.157.22.26
The neighbor’s <ip-addr> must be a valid IP address.
The
neighbor
command has some additional parameters, as shown in the following syntax:
Содержание FastIron Edge Switch X424
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