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BGP and BGP4+ Introduction
Software Reference Supplement for SwitchBlade® x8112, x908, x900 and x610 Series Switches
C613-50032-01 REV D AlliedWare Plus
TM
Operating System - Software Version 5.4.3-2.6 1.35
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:
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:
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)#
network {<ip-prefix/length>|
<ip-network-addr>} [mask
<network-mask>] [route-map
<route-map-name>] [backdoor]
This command determines reachable networks through
backdoor routes when you apply the optional backdoor
parameter.
awplus(config-router)#
distance bgp <ebgp> <ibgp>
<local>
This command assigns a BGP administrative distance.
awplus(config-router)#
bgp default local-preference
<pref-value>
This command changes the default local preference value.
You can use route maps to change the default local preference
of specific paths.