Ip As-Path Access-List - NETGEAR M6100 Series Reference Manual

ip as-path access-list

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 AS path attribute is a list of the autonomous system numbers along the path
to the destination. An AS path 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.
NETGEAR Managed Switch 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.
Table 13 on page 877 lists AS path list regular expression syntax.
Default No AS path lists are configured by default. There are no default values for any of the parameters of this
command.
Format
ip as-path access-list as-path-list-number {permit | deny} regexp
Mode Global Configuration
Parameter Description
as-path-list-number 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.
permit (Optional) Permit routes whose AS Path attribute matches the regular expression.
deny (Optional) Deny routes whose AS Path attribute matches the regular expression.
regexp 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
M6100 Series Switches
Symbol Behavior
* Matches zero or more sequences of the pattern.
[] Designates a range of single-character patterns.
^ Matches the beginning of the input string.
Border Gateway Protocol Commands
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