Setting The Local As Number; Adding A Loopback Interface - Foundry Networks Switch and Router Installation And Configuration Manual

Setting the Local AS Number

The local AS number identifies the AS the Foundry BGP4 router is in. The AS number can be from 1 – 65535.
There is no default. AS numbers 64512 – 65535 are the well-known private BGP4 AS numbers and are not
advertised to the Internet community.
To set the local AS number, use either of the following methods.
USING THE CLI
To set the local AS number, enter commands such as the following:
BigIron(config)# router bgp
BGP4: Please configure 'local-as' parameter in order to enable BGP4.
BigIron(config-bgp-router)# local-as 10
BigIron(config-bgp-router)# write memory
Syntax: [no] local-as <num>
The <num> parameter specifies the local AS number.
USING THE WEB MANAGEMENT INTERFACE
1. Log on to the device using a valid user name and password for read-write access. The System configuration
panel is displayed.
2. Select the Enable radio button next to BGP.
3. Enter the local AS number in the Local AS field.
4. Click the Apply button to apply the changes to the device's running-config file.
5. Select the Save link at the bottom of the dialog. Select Yes when prompted to save the configuration change
to the startup-config file on the device's flash memory.

Adding a Loopback Interface

You can configure the router to use a loopback interface instead of a specific port 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 router and its 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 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, use one of the following methods.
USING THE CLI
To add a loopback interface, enter commands such as those shown in the following example:
BigIron(config-bgp-router)# exit
BigIron(config)# int loopback 1
BigIron(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.
December 2000
Configuring BGP4
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