H3C Technologies H3C S10500 Series Switches - Manual (Page 367)

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An IP prefix list is configured to match the destination address of routing information. You can use the
gateway option to allow only routing information from certain routers to be received. For gateway option
information, see the chapters “RIP configuration” and “OSPF configuration.”
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.
For more information about AS-PATH list, see the chapter “BGP configuration.”
Community list
A community list, configured based on the BGP community attribute, can only be used to match BGP
routing information.
For more information about community list, see the chapter “BGP configuration.”
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.
For more information about extended community list, see MPLS Configuration Guide.
Routing policy
A routing policy is used to match routing information and modify the attributes of permitted routes. It can
reference the filters to define its own match criteria.
A routing policy can comprise multiple nodes, which are in logic OR relationship. Each routing policy
node is a match unit, and a node with a smaller number is matched first. Once a node is matched, the
routing policy is passed and the packet will not go to the next node.
A routing policy node comprises a set of if-match, apply, and continue clauses.
• The if-match clauses define the match criteria. The matching objects are some attributes of routing
information. The if-match clauses of a routing policy node is in a logical AND relationship. A
packet must match all the if-match clauses of the node to pass it.
• The apply clauses of the node specify the actions to be taken on the permitted packets, such as
modifying a route attribute.
• The continue clause specifies the next routing policy node to be matched. With this clause
configured, when a route matches the current routing policy node, it continues to match against the
specified next node in the same routing policy. The continue clause combines the if-match and
apply clauses of the two nodes to improve flexibility of the routing policy.
Use the following guidelines when configuring if-match, apply, and continue clauses:
• If you want to implement route filtering only, you do not need to configure apply clauses.
• If you do not configure any if-match clauses for a permit-mode node, the node permits all routes to
pass.
• Configure a permit-mode node containing no if-match or apply clauses behind multiple deny-mode
nodes to allow unmatched routes to pass.