Applications Of Routing Policy - H3C S7500 Series Operation Manual

Operation Manual – Routing Protocol
H3C S7500 Series Ethernet Switches
when 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 the
node is successful, that is, configuration to be performed for the attributes of routing
information.
The relationships among different nodes in a route-policy are "OR". The system will
examine the nodes in the route-policy in sequence. Once the route passes a node in
the route-policy, it will pass the matching test of the route-policy without entering the
test of the next node.
II. ACL
Normally, a basic ACL is used to filter routing information. You can specify a range of
IP addresses or subnets when defining a basic ACL to match the destination network
segment address or the next-hop address of routing information. If an advanced ACL
is used, the specified range of source addresses will be used for matching.
III. ip-prefix
An ip-prefix plays a role similar to ACL. But it is more flexible than ACL and easier to
understand. When ip-prefix is applied to filtering routing information, its matching
object 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 network
prefix form. An index-number specifies the matching sequence in the ip-prefix.
During the matching, the router checks items identified by index-number in ascending
order. Once an item is met, the ip-prefix filtering is passed and no other item will be
checked.
IV. as-path
An as-path is an access control list of autonomous system paths only used for BGP to
match AS paths. A BGP routing information packet includes an AS path field which
records the AS paths that the routing information passes through during the exchange
process.
V. community-list
A community-list is only used for BGP to match community attributes. A BGP routing
information packet contains a community attribute field used to identify a community.

7.1.2 Applications of Routing Policy

The following are main applications of routing policy:
When a routing protocol advertises or receives routing information, it adopts
routing policies to filter routing information, so as to receive or advertise those
routing information meeting the given conditions.
Chapter 7 IP Routing Policy Configuration
7-2