H3C Technologies H3C S7500E Series Switches - Manual (Page 359)

12-2
1) Define some filters based on the attributes of routing information, such as destination address,
and the advertising router’s address.
2) Then apply the filters to the route policy.
You can use multiple filters flexibly to define match criteria. For detailed information, see Filters .
Filters
There are six types of filters: ACL, IP prefix list, AS path ACL, community list, extended community list
and route policy.
ACL
ACL involves IPv4 ACL and IPv6 ACL. An ACL is configured to match the destinations or next hops of
routing information.
For ACL configuration, see ACL configuration in the ACL and QoS Configuration Guide.
IP prefix list
IP prefix list involves IPv4 prefix list and IPv6 prefix list.
An IP prefix list is configured to match the destination address of routing information. Moreover, you
can use the gateway option to allow only routing information from certain routers to be received. For
gateway option information, see RIP Configuration Commands and OSPF Configuration Commands
in the Layer 3 - IP Routing Command Reference.
An IP prefix list, identified by name, can comprise multiple items. Each item, identified by an index
number, can specify a prefix range to match. An item with a smaller index number is matched first. If
one item is matched, the IP prefix list is passed, and the packet will not go to the next item.
AS-PATH list
An AS-PATH list, configured based on the BGP AS PATH attribute, can only be used to match BGP
routing information.
Community list
A community list, configured based on the BGP community attribute, can only be used to match BGP
routing information.
Extended community list
An extended community list, configured based on the BGP extended community attribute
(Route-Target for VPN, and Source of Origin), can only be used to match BGP routing information.
Route policy
A route policy is used to match routing information and modify the attributes of permitted routes. It can
reference the above mentioned filters to define its own match criteria.
A route policy can comprise multiple nodes, which are in logic OR relationship. Each route policy node
is a match unit, and a node with a smaller number is matched first. Once a node is matched, the route
policy is passed and the packet will not go to the next node.
A route policy node comprises a set of if-match and apply clauses.
z The if-match clauses define the match criteria. The matching objects are some attributes of
routing information. The if-match clauses of a route policy node is in logical AND relationship.
That is, a packet must match all the if-match clauses of the node to pass it.
z The apply clauses of the node specify the actions to be taken on the permitted packets, such as
route attribute modification.