3Com Switch 8800 Configuration Guide Chapter 22 IP Routing Policy Configuration22-722.2.2 Configuring ip-prefixz A prefix-list is identified by an ip-prefix-name. Each IP prefix-list may includemultiple entries each specifying an IP prefix matching range. IP prefix entries areidentified by index-numbers. The order in which IP prefix entries are matchedagainst depends on the order of their index numbers.Perform the following configuration in system view.Table 22-4 Define prefix-listOperation CommandDefine prefix-listip ip-prefix ip-prefix-name [ index index-number ] { permit |deny } network len [ greater-equal greater-equal ][ less-equal less-equal ]Remove prefix-list undo ip ip-prefix ip-prefix-name [ index index-number |permit | deny ]During the matching, the router checks list items identified by the index-number in theascending order. If only one list item meets the condition, it means that it has passedthe ip-prefix filtering (will not enter the testing of the next list item).Note that if more than one ip-prefix item are defined, then the match mode of at leastone list item should be the permit mode. The list items of the deny mode can be firstlydefined to rapidly filter the routing information not satisfying the requirement, but if allthe items are in the deny mode, no route will pass the ip-prefix filtering. You can definean item of permit 0.0.0.0/0 greater-equal 0 less-equal 32 after the multiple list items inthe deny mode so as to let all the other routes pass.22.2.3 Configuring the AS Path ListThe routing information packet of the BGP includes an autonomous system pathdomain. The as path-list can be used to match with the autonomous system pathdomain of the BGP routing information so as to filter the routing information, which doesnot conform to the requirements.Perform the following configuration in the system view:Table 22-5 Define the AS path listOperation CommandDefine the AS path list ip as-path-acl acl-number { permit |deny } as-regular-expressionDelete the specified AS path list undo ip as-path-acl acl-numberBy default, no AS path list is defined.
