Operation Manual – Routing ProtocolH3C S7500 Series Ethernet Switches Chapter 7 IP Routing Policy Configuration7-2when all the matching conditions specified by all the if-match clauses are satisfied.The apply clauses specify the actions performed after a matching test against thenode is successful, that is, configuration to be performed for the attributes of routinginformation.The relationships among different nodes in a route-policy are “OR”. The system willexamine the nodes in the route-policy in sequence. Once the route passes a node inthe route-policy, it will pass the matching test of the route-policy without entering thetest of the next node.II. ACLNormally, a basic ACL is used to filter routing information. You can specify a range ofIP addresses or subnets when defining a basic ACL to match the destination networksegment address or the next-hop address of routing information. If an advanced ACLis used, the specified range of source addresses will be used for matching.III. ip-prefixAn ip-prefix plays a role similar to ACL. But it is more flexible than ACL and easier tounderstand. When ip-prefix is applied to filtering routing information, its matchingobject is the destination address information field of routing information.An ip-prefix is identified by name. An ip-prefix includes multiple items, and each item,identified by an index-number, can independently specify the match range in networkprefix form. An index-number specifies the matching sequence in the ip-prefix.During the matching, the router checks items identified by index-number in ascendingorder. Once an item is met, the ip-prefix filtering is passed and no other item will bechecked.IV. as-pathAn as-path is an access control list of autonomous system paths only used for BGP tomatch AS paths. A BGP routing information packet includes an AS path field whichrecords the AS paths that the routing information passes through during the exchangeprocess.V. community-listA community-list is only used for BGP to match community attributes. A BGP routinginformation packet contains a community attribute field used to identify a community.7.1.2 Applications of Routing PolicyThe following are main applications of routing policy:z When a routing protocol advertises or receives routing information, it adoptsrouting policies to filter routing information, so as to receive or advertise thoserouting information meeting the given conditions.
