3Com Switch 7750 Configuration Guide Guide

368 CHAPTER 37: IP ROUTING POLICY CONFIGURATION
independently specify the match range in network prefix form. Index-numbers
specify the matching order of the items in the ip-prefix.
Perform the following configuration in system view.
During a matching test, the router checks the items in the ascending order of their
index-numbers. Once an item is met, the ip-prefix filtering is passed and no other
item will be checked.
n
Among the items defined in an IP prefix list, at least one item should be in permit
mode. The items in deny mode can be used to quickly filter out undesired routing
information. But if all the items are in deny mode, no route will pass the filter of
the IP prefix list. You can define an item permit 0.0.0.0/0 greater-equal 0
less-equal 32 after the deny-mode items to permit all other routes to pass
through.
AS Path List
Configuration
A BGP routing information packet contains an AS path field. AS path list can be
used to match the AS path field in BGP routing information to filter out the
routing information that does not match.
You can perform the following configuration in system view.
By default, no AS path list is defined.
Community List
Configuration
In BGP, community attributes are optional transitive. Some community attributes
are globally recognized and they are called standard community attributes. Some
are for special purposes and they can be customized.
A route can have one or more community attributes. The speaker of multiple
community attributes of a route can act based on one, multiple or all attributes. A
router can decide whether to change community attributes before forwarding a
route to other peer entity.
Community list is used to identify community information. It falls in to two types:
basic community list and advanced community list. The former one’s value ranges
from 1 to 99, and the latter one’s ranges from 100 to 199.
Tabl e 294 Define an IP prefix list
Operation Command Description
Enter system view system-view -
Define an IP prefix list
ip ip-prefix ip-prefix-name [
index index-number ] {
permit | deny } network len [
greater-equal greater-equal |
less-equal less-equal ]*
Optional
Tabl e 295 AS path list configuration
Operation Command Description
Enter system view system-view -
Configure AS path list
ip as-path-acl acl-number {
permit | deny }
as-regular-expression
Optional