3Com SuperStack 4 Configuration Manual page 144

156 C 6: IP R
HAPTER OUTING
Configuring an IP
Routing Policy
P O
ROTOCOL PERATION
actions that are performed after the node match test concerning the attribute
settings of the route information.
The comparisons of different nodes in a route policy uses a Boolean "OR"
statement. The system examines the nodes in the route policy in sequence. Once
the route is permitted by a single node in the route-policy, the route passes the
matching test of the route policy without attempting the test of the next node.
ACL
The access control list (ACL) used by the route policy can be divided into three
types: advanced ACL, basic ACL and interface ACL.
A basic ACL is usually used for routing information filtering. When the user
defines the ACL, the user must define the range of an IP address or subnet for the
destination network segment address, or the next-hop address of the routing
information. If an advanced ACL is used, perform the matching operation by the
specified source address range.
For details of ACL configuration, refer to Chapter 7, Using QoS/ACL Commands.
IP Prefix
The function of the IP Prefix is similar to that of the ACL, but it is more flexible and
easier for users to understand. When the IP Prefix is applied to routing information
filtering, its matching objects are the destination address information and the
domain of the routing information. In addition, in the IP Prefix, you can specify the
options and require it to receive only the routing information distributed
gateway
by some certain routers.
An IP Prefix is identified by the ip-prefix name. Each IP Prefix can include multiple
list items, and each list item can specify the match range of the network prefix
forms, and is identified with an index-number. The index-number designates the
matching check sequence in the IP Prefix.
During the matching, the router checks list items identified by the
sequence-number in ascending order. Once a single list item meets the condition,
it means that it has passed the ip-prefix filtering and does not enter the testing of
the next list item.
Configuring a routing policy includes tasks described in the following sections:
Defining a Route Policy
■
Defining If-match Clauses for a Route-policy
■
Defining Apply Clauses for a Route Policy
■
Importing Routing Information Discovered by Other Routing Protocols
■
Defining IP Prefix
■
Configuring the Filtering of Received Routes
■
Configuring the Filtering of Distributed Routes
■
Defining a Route Policy
A route policy can include multiple nodes. Each node is a unit for the matching
operation. The nodes are tested against the .
node_number