H3C S3610-28P Operation Manual page 545

Operation Manual – IPv4 Routing
H3C S3610&S5510 Series Ethernet Switches
address and so on. The match criteria can be set beforehand and then apply them to a
routing policy for route distribution, reception and redistribution.
6.1.2 Filters
Routing protocols can use six filters: ACL, IP prefix list, AS path ACL, community list,
extended community list and routing policy.
I. ACL
ACL involves IPv4 ACL and IPv6 ACL. When defining an ACL, you can specify IP
addresses and prefixes to match destinations or next hops of routing information.
For ACL configuration, refer to ACL configuration in the Security Volume.
II. IP prefix list
IP prefix list plays a role similar to ACL, but it is more flexible than ACL and easier to
understand. When an IP prefix list is applied to filtering routing information, its matching
object is the destination address of routing information. Moreover, you can specify the
gateway option to indicate that only routing information advertised by certain routers
will be received.
An IP prefix list is identified by name. Each IP prefix list can comprise multiple items,
and each item, which is identified by an index number, can specify a matching range in
the network prefix format. The index number indicates the matching sequence of items
in the IP prefix list.
During matching, the router compares the packet with the items in the ascending order.
If one item is matched, the IP prefix list filter is passed, and the packet will not go to the
next item.
III. AS-path
AS path is only applicable to BGP. There is an AS-path field in the BGP packet. An AS
path list specifies matching conditions according to the AS-path field.
IV. Community list
Community list only applies to BGP. The BGP packet contains a community attribute
field to identify a community. A community list specifies matching conditions based on
the community attribute.
V. Extended community list
Extended community list (extcommunity-list) applies to BGP only. It involves two
attributes: Route-Target extcommunity for VPN, Source of Origin extcommunity. An
extcommunity-list specifies matching conditions according to the two attributes.
Chapter 6 Routing Policy Configuration
6-2