3Com 5500 SI - Switch - Stackable, Руководство по настройке

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IP Routing Policy 259
and the matching objects are attributes of routing information. The relationship of
if-match
clauses for a node uses a series of Boolean “AND” statements. As a result,
a match is found unless all the matching conditions specified by the
if-match
clauses are satisfied. The
apply
clause specifies the 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
gateway
options and require it to receive only the routing information distributed 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 an IP
Routing Policy
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