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Matching Rule

A routing map is a routing policy consists of N orders nodes of match and set statements (N ≥ 1). Each node has its own set of match clauses that must be matched in order to accept a policy. TheThe match clauses define matching rules related to route attributes and filters. The system checks routes in the orders of a routing map in ascending order of order IDs.

When a route matches all match clauses in a order, the route enters the matching mode without other nodes checkingmatching modes defined in matching-policy and set-action clauses and stops checking match clauses in other nodes. The two supported matching modes are:

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If a route does not match any match clause in a node, the route is passed to the next node. If the route does not match any node, the route is filtered out.

Note that, in all configurations, matching-policy is a required clause to enable a route map. Other clauses are optional.

The default action of a route-map, if no entries match, is to deny. I.e. a route-map essentially has as its last entry an empty deny entry, which matches all routes. To change this behaviour, one must specify an empty permit entry as the last entry in the route-map.

Filters

There are different filters specified in match clauses in a routing policy which including IP prefix list, AS_Path filter, community filter, extended community filter, and large community filter. These filters have their own matching rules and modes and can be used independently to filter routes in specific situations. The following offers a brief explanation to each of these filters.

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The community attribute identifies a group of routes with the same properties. For details about the community attribute, see Configuring the BGP Community Attribute.

Extended Community Filter

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The large community filter uses the large community attribute of BGP to filter routes. The commands set routing large-community-list {standard <large-community-list-name>| seq-standard<integer>} {deny|permit} [large-community <large-community-number>]  and set routing large-community-list {expanded <large-community-list-name>| seq-expanded <integer>} {deny|permit} <line> can be used to define the large community list.

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