H3C Technologies H3C S12500 Series Switches - Manual (Page 420)

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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 "Configuring BGP."
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 "Configuring BGP."
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 to modify the attributes of permitted routes. It
can reference the previously mentioned filters to define its own match criteria.
A routing policy can comprise multiple nodes, which are in a logical 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. That is,
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 route
attribute modification.
• The continue clause specifies the next policy node to be matched. With this clause configured,
when a route matches the current policy node, it continues to match against the specified next node
in the same routing policy. The continue clause thus combines the if-match and apply clauses of the
two nodes to improve flexibility of the routing policy.
When you configure if-match, apply, and continue clauses, follow these guidelines:
• 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.