Dell N3200-ON Networking N-Series Switches User Guide version 6.8.0 - Page 1376

• If the individual routes have communities and the aggregate does not have the ATOMIC_AGGREGATE attribute set, the aggregate is advertised with the union of the communities from the individual routes. If the aggregate carries the ATOMIC_AGGREGATE attribute, the aggregate is advertised with no communities. Dell Networking BGP never aggregates paths with unknown attributes. By default, Dell Networking BGP does not aggregate paths with different MEDs, but there is a configuration option to allow this. Routing Policy Route maps are used to implement redistribution policy, i.e., they are used to filter routes and change route attributes. Route maps may be applied in the inbound direction (before the P2 decision process) or in the outbound direction (after best route selection but before redistribution to peer routers). In either direction, the list of configured route maps is processed in order of increasing sequence number. Match clauses in a route map are processed as a logical AND, i.e., all match clauses in a route-map must match for the route to be processed. If a route matches all relevant match clauses in a route map, the route is permitted or denied and route-map list processing ceases for that route. (Some match clauses are irrelevant to routing policy, e.g., match length). ACLs are not supported for matching prefixes when filtering routes. Use the ip prefix-list command instead. Matching on AS numbers, community, or extended communities is also supported. In processing the list of route maps, each route map is processed individually. When a match occurs, if the route is permitted, the set clauses are processed and list processing ceases. If the route is denied, no set clauses are processed and list processing ceases. If no match occurs, list processing continues with the next highest numbered route map. Unlike PBR, routing policy route maps implement an implicit deny at the end of the last route map that filters out all routes. Routes that do not match any match clause reach the end of the route map list and are removed. An empty route map has a defined action. An deny route map with no match clause matches all routes and does not perform any set actions since the action is deny. Processing of the route-map list ceases. An empty permit route map permits all routes, performs any set clauses, and stops processing of the route-map list since it matched a route. 1376 BGP