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100 CHAPTER 5: IP ROUTING PROTOCOL OPERATION
A basic ACL is usually used for routing information filtering. When the user
defines the ACL, the user defines the range of an IP address, 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. Layer-2 ACLs
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 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 a 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 for Filtering Received Routes
■ Configuring for Filtering Distributed Routes
■ Displaying and Debugging the Routing Policy
Defining a Route Policy
A route policy can include multiple nodes. Each node is a unit for the matching
operation. The nodes are tested again by sequence-number.
Perform the following configurations in system view.
Table 100 Defining a Route Policy
Operation Command
Enter Route policy view route-policy route-policy-name {
permit | deny } node {
node-number }
Remove the specified route-policy undo route-policy
route-policy-name [ permit | deny
| node node-number ]