Allied Telesis X8100 Other Uses of Route Maps, neighbor default-originate, network, show ip bgp

Other Uses of Route Maps

Other Uses of Route Maps

Route maps are used in some contexts other than filtering routes. Let us look briefly at some of the other contexts in which they are used.

neighbor default-originate

The command neighbor default-originate instructs BGP to send a default route to a neighbor. This command includes a parameter for specifying a route map.

The route map parameter specifies criteria that must be fulfilled before the switch will advertise the default route to the neighbor. This lets you configure the switch so that it only acts as the default gateway for a neighbor if it has learned a route that makes it a suitable default gateway for that neighbor.

Specifically, the switch must have learnt a route that matches the permit criteria in the route map. If the switch does not know of any routes that match the permit criteria in the route map, then it will not advertise the default route.

neighbor unsuppress-map

When the aggregate-addresscommand is used with the summary-onlyoption, the more specific routes of the aggregate are suppressed to all neighbors. If you want to selectively leak some more-specific routes to a particular neighbor, then this is achieved by using the command neighbor unsuppress-map.

A required parameter on this command is the route map that specifies the set of more- specific routes to leak. Any route that matches permit criteria in the route map will be leaked.

network

The network command is used in BGP to selectively redistribute particular routes. Instead of saying “redistribute all static routes” or “redistribute all connected routes”, the network command says “redistribute this particular route”. Of course, the route has to be in the routing table before it can be redistributed, so the network command does not say “always import this route in BGP”, it says “if this route is in the routing table, then import it into BGP”.

As with other acts of redistribution, the network command has an optional route map parameter. This lets you set attributes on the route advertised by the network command. You could use the route map for filtering the network, but it would be a little pointless to even configure the redistribution of this network if the associated route map simply dropped the route.

show ip bgp

The show ip bgp command takes an optional route map parameter. The effect of specifying the route map on the command is that the output shows information only on routes that match permit criteria on the route map.

Use Route Maps and Other Filters to Filter and Alter BGP and OSPF Routes Page 47