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Setting Global BGP Parameters Configuring BGP
page 4-22 OmniSwitch 6800/6850/9000 Advanced Routing Configuration Guide December 2007
Enabling AS Path Comparison
The AS path is a route attribute that shows the sequence of ASs through which a route has traveled. For
example if a path originated in AS 1, then went through AS 3, and reached its destination in AS 4, then the
AS path would be:
4 3 1
A shorter AS path is preferred over a longer AS path. The AS path is always advertised in BGP route
updates, however you can control whether BGP uses this attribute when comparing routes. The length of
the AS path may not always indicate the effectiveness for a given route. For example, if a route has an AS
path of:
1 3 4
using only T1 links, it might not be a faster path than a longer AS path of:
2 4 5 7
that uses only DS-3 links.
By default AS path comparison is enabled. You can disable it by specifying:
-> no ip bgp bestpath as-path ignore
This command requires that you first disable the BGP protocol. If BGP were already enabled, you would
actually need to issue two commands to turn off AS path comparison:
-> ip bgp status disable
-> no ip bgp bestpath as-path ignore