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Configuring BGP Routing Policies
OmniSwitch 6800/6850/9000 Advanced Routing Configuration Guide December 2007 page 4-47
Creating a Prefix List Policy
Prefix policies filter routes based on network addresses and their masks. You can also set prefix upper and
lower limits to filter a range of network addresses.
To create a prefix list policy:
1 Name the policy and specify the IP network address and mask using the ip bgp policy prefix-list
command, as shown:
-> ip bgp policy prefix-list prefixfilter 12.0.0.0 255.0.0.0
Prefix policy prefixfilter now filters routes that match the network address 12.0.0.0 with a mask of
255.0.0.0.
2 Set the policy action using the ip bgp policy prefix-list action command. The policy action either
permits or denies routes that match the filter. Permitted routes are advertised, while denied routes are not.
For example:
-> ip bgp policy prefix-list prefixfilter 12.0.0.0 255.0.0.0 action deny
Prefix policy prefixfilter now denies routes that match the network address 12.0.0.0 with a mask of
255.0.0.0.
3 Optionally, you can set a lower prefix limit on the addresses specified in the policy using the ip bgp
policy prefix-list ge command. For example:
-> ip bgp policy prefix-list prefixfilter 14.0.0.0 255.0.0.0 ge 16
Prefix policy prefixfilter now denies routes after 14.0.0.0/16.
4 Optionally, you can set an upper prefix limit on the addresses specified in the policy using the ip bgp
policy prefix-list le command. For example:
-> ip bgp policy prefix-list prefixfilter 14.0.0.0 255.0.0.0 le 24
Prefix policy prefixfilter now denies routes between 14.0.0.0/16 and 14.0.0.0/24
Creating a Route Map Policy
Route map policies let you amalgamate the other policy types together, as well as add various other filters.
For example, you could have a route map policy that includes both an AS path policy and a community
policy.
To create a route map policy:
1 Name the route map policy and assign it a sequence number using the ip bgp policy route-map
command. The sequence number allows for multiple instances of a policy, and orders the route map poli-
cies so that a lower sequence number is applied first. For example:
-> ip bgp policy route-map mapfilter 1
Route map policy mapfilter is now ready.