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Configuring BGP Setting Global BGP Parameters
OmniSwitch 6800/6850/9000 Advanced Routing Configuration Guide December 2007 page 4-21
Setting the Router AS Number
The router takes a single Autonomous System (AS) number. You can assign one and only one AS number
to a router using the ip bgp autonomous-system command. That same router may contain peers that
belong to a different AS than the AS you assign your router. In such a case these BGP peers with a differ-
ent AS would be considered external BGP (EBGP) peers and the communication with those peers would
be EBGP.
The following command would assign an AS number of 14 to a router:
-> ip bgp autonomous-system 14
This command requires that you first disable the BGP protocol. If BGP were already enabled, you would
actually need to issue two commands to assign the router’s AS number to 14:
-> ip bgp status disable
-> ip bgp autonomous-system 14
Setting the Default Local Preference
A route’s local preference is an important attribute in the path selection process. In many cases it will be
the most important criteria in determining the selection of one route over another. A route obtains its local
preference in one of two ways:
• By taking the default local preference established globally in the router.
• By having this default local preference manipulated by another command. The BGP peer, aggregate
route, and network commands allow you to assign a local preference to a route. It is also possible to
manipulate the local preference of a route through BGP policy commands.
The local preference in the router is set by default to 100. If you want to change this value, use the
ip bgp default local-preference command. For example, if you wanted to change the default local prefer-
ence for all routes to 200, you would issue the following command:
-> ip bgp default local-preference 200
This command requires that you first disable the BGP protocol. If BGP were already enabled, you would
actually need to issue two commands to change the default local preference to 200:
-> ip bgp status disable
-> ip bgp default local-preference 200