6-2IP-prefix listIP-prefix list plays a role similar to ACL. But it is more flexible than ACL and easier to understand. WhenIP-prefix list is applied to filter routing information, its matching object is the destination address field inrouting information. Moreover, with IP-prefix list, you can use the gateway option to specify that onlyrouting information advertised by certain routers will be received.An IP-prefix list is identified by its IP-prefix name. Each IP-prefix list can contain multiple entries, andeach entry, identified by an index-number, can independently specify the match range in the networkprefix form. An index-number specifies the matching sequence in the IP-prefix list.There is an OR relationship between entries. During the matching, the router checks entries identifiedby index-number in ascending order. Once an entry is matched, the IP-prefix list filtering is passed andno other entries will be checked.As-pathAs-path is an access control list of autonomous system path. It is only used in BGP to define thematching conditions about AS path. An as-path contains a series of AS paths which are the records ofrouting information passed paths during BGP routing information exchange.Community-listCommunity-list is only used to define the matching conditions about COMMUNITY attributes in BGP. ABGP routing information packet contains a COMMUNITY attribute field used to identify a community.Routing policyA routing policy is used to match some attributes with given routing information and the attributes of theinformation will be set if the conditions are satisfied.A routing policy can comprise multiple nodes. Each node is a unit for matching test, and the nodes willbe matched in ascending order of their node numbers. Each node comprises a set of if-match andapply clauses. The if-match clauses define the matching rules. The matching objects are someattributes of routing information. The relationship among the if-match clauses for a node is “AND”. As aresult, a matching test against a node is successful only when all the matching conditions specified bythe if-match clauses in the node are satisfied. The apply clauses specify the actions performed after amatching test against the node is successful, and the actions can be the attribute settings of routinginformation.There is an OR relationship between different nodes in a routing policy. As a result, the systemexamines the nodes in the routing policy in sequence, and once the route matches a node in the routingpolicy, it will pass the matching test of the routing policy without entering the test of the next node.IP Routing Policy Configuration Task ListComplete the following tasks to configure an IP routing policy:Task RemarksDefining a Routing Policy RequiredRouting Policy Configuration Defining if-match Clauses andapply Clauses RequiredIP-Prefix Configuration RequiredAS Path List Configuration Required
