H3C S7500E Series Operation Manual page 555

Operation Manual – IPv6 Routing
H3C S7500E Series Ethernet Switches
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 IPv6 BGP. There is an AS-path field in the IPv6 BGP
packet. An AS path list specifies matching conditions according to the AS-path field.
IV. Community list
Community list only applies to IPv6 BGP. The IPv6 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 IPv6 BGP only. It is used for
Route-Target extcommunity for VPN.
VI. Routing policy
A routing policy is used to match against some attributes in given routing information
and modify the attributes of the information if match conditions are satisfied. It can
reference the above mentioned filters to define its own match criteria.
A routing policy can comprise multiple nodes, which are in logic OR relationship. Each
node is a match unit, and the system compares each node to a packet in the order of
node sequence number. Once a node is matched, the routing policy is passed and the
packet will not go through the next node.
Each node comprises a set of if-match and apply clauses. The if-match clauses
define the match criteria. The matching objects are some attributes of routing
information. The different if-match clauses on a node is in logical AND relationship.
Only when the matching conditions specified by all the if-match clauses on the node
are satisfied, can routing information pass the node. The apply clauses specify the
actions to be performed after the node is passed, concerning the attribute settings for
routing information.
6.1.3 Routing Policy Application
A routing policy is applied in two ways:
When redistributing routes from other routing protocols, a routing protocol accepts
only routes passing the routing policy.
Chapter 6 Routing Policy Configuration
6-2