3com 3031 Instruccion De Instalación

C

HAPTER

 43: IP R

OUTING

 P

OLICY

 C

ONFIGURATION

Normally, basic ACL is adopted to filter routing information. The user specifies a 
range of IP addresses or subnets when defining ACL so as to match the 
destination network segment address or next-hop address of routing information. 
If advanced ACL is adopted, specified range of source addresses will be used for 
matching.

For ACL configuration, refer to Chapter 59 “Firewall Configuration”.

The IP-prefix plays a role similar to ACL. But it is more flexible than ACL and easier 
to understand. When IP-prefix is applied for filtering of routing information, its 
matching object is the destination address information field of routing 
information. Moreover, for IP-prefix, the user can specify the gateway option so as 
to indicate that only routing information advertised by certain routers will be 
received.

An IP-prefix is identified by the ip-prefix name. Each IP-prefix can include multiple 
items, and each item, which is identified by an index-number, can independently 
specify the matching range of the network prefix forms. The index-number 
specifies the matching sequence in the IP-prefix list.

During the matching, the router checks list items identified by the index-number in 
the ascending order. If only one list item meets the condition, it means that it has 
passed the IP-prefix filtering (will not enter the testing of the next list item).

AS-path only applies to BGP. In the BGP routing information packet, there is an 
AS-path field (During BGP routing information exchange, the AS path where 
routing information passes will be recorded in the field). As-path specifies 
matching conditions according to the AS-path field.

The definition of the AS-path has already been implemented in the BGP 
configuration. For the related configurations, please refer to the 

 

command in Chapter 42“BGP Configuration”.

The community-list only applies to BGP. The routing information packet of the BGP 
includes a community attribute domain to identify a community. Targeting at the 
community attribute, the community-list specifies the match condition.

The definition of the community-list has already been implemented in the BGP 
configuration. For the relevant configurations, please refer to the 

command in Chapter 42“BGP Configuration”.

The routing policy configuration includes:

■

Define a route-policy

■

Define if-match clauses for a route-policy

■

Define apply clauses for a route-policy

■

Import the routes of other routing protocols

■

Define IP prefix list