D-Link DXS-5000-54S Emulator - Page 1146

5000 Series Layer 2/3 Managed Data Center Switch CLI Reference Guide To create an AS-PATH access list, use the ip as-path access-list command in Global Configuration mode. An AS-PATH access list filters BGP routes on the AS-PATH attribute of a BGP route. The ASPATH attribute is a list of the autonomous system numbers along the path to the destination. An ASPATH access list is an ordered sequence of statements. Each statement specifies a regular expression and a permit or deny action. If the regular expression matches the AS-PATH of the route expressed as an ASCII string, the route is considered a match and the statement's action is taken. An AS-PATH list has an implicit deny statement at the end. If a path does not match any of the statements in an AS-PATH list, the action is considered to be deny. Once you have created an AS-PATH list, you cannot delete an individual statement. If you want to remove an individual statement, you must delete the AS-PATH list and recreate it without the statement to be deleted. Statements are applied in the order in which they are created. New statements are added to the end of the list. The statement with the first matching regular expression is applied. D-LINK OS allows configuration of up to 128 AS-PATH access lists, with up to 64 statements each. To enter the question mark within a regular expression, you must first enter CTRL-V to prevent the CLI from interpreting the question mark as a request for help. See Table 13 for a listing of AS-PATH list regular expression syntax. Use the no command to delete an AS-PATH access list. {permit | deny} regexp no ip as-path access-list as-path-list-number Parameters as-path-list-number permit deny regexp A number from 1 to 500 uniquely identifying the list. All AS-PATH access list commands with the same as-path-list-number are considered part of the same list. (Optional) Permit routes whose AS-PATH attribute matches the regular expression. (Optional) Deny routes whose AS-PATH attribute matches the regular expression. A regular expression used to match the AS-PATH attribute of a BGP path where the AS-PATH is treated as an ASCII string. Table 13: AS-PATH Regular Expression Syntax Special Character asterisk brackets caret dollar sign hyphen period Symbol * [] ^ $ - . Behavior Matches zero or more sequences of the pattern. Designates a range of single-character patterns. Matches the beginning of the input string. Matches the end of the input string. Separates the end points of a range. Matches any single character, including white space. 1140