Allied Telesis VERSION 5.4.3-2.6, BGP4 manual BGP Optimization, How to determine Backdoor Routes

BGP and BGP4+ Introduction

BGP Optimization

How to determine Backdoor Routes

You can determine which networks are reachable by using a backdoor route that the border router should use. A backdoor network is treated as a local network, except that it is not advertised. To configure backdoor routes, use the network backdoor command, beginning in Router Configuration mode:

awplus(config-router)#

network {<ip-prefix/length>This command determines reachable networks through <ip-network-addr>} [mask backdoor routes when you apply the optional backdoor

<network-mask>][route-mapparameter. <route-map-name>] [backdoor]

How to set the BGP Administrative Distance

Administrative Distance is a measure of the preference of different routing protocols. BGP uses three different administrative distances: external, internal, and local. Routes learned through external BGP are given the external distance, routes learned with iBGP are given the internal distance, and routes that are part of this autonomous system are given the local distance. To assign a BGP administrative distance, use the following command in Router Configuration mode:

awplus(config-router)#

distance bgp <ebgp> <ibgp> This command assigns a BGP administrative distance.

<local>

Changing administrative distance of BGP routes may cause issues so is not recommended. The external distance should be lower than any other dynamic routing protocol, and the internal and local distances should be higher than any other dynamic routing protocol.

How to change BGP default local preference value

You can define a particular path as more preferable or less preferable than other paths by changing the default local preference value of 100. To assign a different default local preference value, use the following command in Router Configuration mode:

awplus(config-router)#

bgp default local-preferenceThis command changes the default local preference value. <pref-value>You can use route maps to change the default local preference

of specific paths.

	Software Reference Supplement for SwitchBlade® x8112, x908, x900 and x610 Series Switches
C613-50032-01 REV D	AlliedWare PlusTM Operating System - Software Version 5.4.3-2.6	1.35