Users Guide

To configure a prefix-list, use commands in PREFIX-LIST and ROUTER-BGP modes. Create the prefix-list in PREFIX-LIST mode and
assign that list to commands in ROUTER-BGP modes.
Route-maps
Route-maps are a series of commands that contain a matching criterion and action. They change the packets meeting the matching
criterion. ACLs and prefix-lists can only drop or forward the packet or traffic while route-maps process routes for route redistribution. For
example, use a route-map to filter only specific routes and to add a metric.
• Route-maps also have an implicit deny. Unlike ACLs and prefix-lists where the packet or traffic drops, if a route does not match the
route-map conditions, the route does not redistribute.
• Route-maps process routes for route redistribution. For example, to add a metric, a route-map can filter only specific routes. If the
route does not match the conditions, the route-map decides where the packet or traffic drops. The route does not redistribute if it
does not match.
• Route-maps use commands to decide what to do with traffic. To remove the match criteria in a route-map, use the no match
command.
• In a BGP route-map, if you repeat the same match statements; for example, a match metric, with different values in the same
sequence number, only the last match and set values are taken into account.
Configure match metric
OS10(config)# route-map hello
OS10(conf-route-map)# match metric 20
View route-map
OS10(conf-route-map)# do show route-map
route-map hello, permit, sequence 10
Match clauses:
metric 20
Change match
OS10(conf-route-map)# match metric 30
View updated route-map
OS10(conf-route-map)# do show route-map
route-map hello, permit, sequence 10
Match clauses:
metric 30
To filter the routes for redistribution, combine route-maps and IP prefix lists. If the route or packet matches the configured criteria, OS10
processes the route based on the
permit or deny configuration of the prefix list.
When a route-map and a prefix list combine:
• For a route map with the permit action:
• If a route matches a prefix-list set to deny, the route is denied
• If a route matches a prefix-list set to permit, the route is permitted and any set of actions apply
• For a route map with the deny action:
• If a route matches a prefix-list set to deny, the route is denied
• If a route matches a prefix-list set to permit, the route is permitted and any set of actions apply
View both IP prefix-list and route-map configuration
OS10(conf-router-bgp-neighbor-af)# do show ip prefix-list
ip prefix-list p1:
seq 1 deny 10.1.1.0/24
seq 10 permit 0.0.0.0/0 le 32
ip prefix-list p2:
seq 1 permit 10.1.1.0/24
seq 10 permit 0.0.0.0/0 le 32
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Access Control Lists