Cabletron Systems SmartSwitch manual 132

Chapter 10: BGP Configuration Guide

( aspath_regexp )

Parentheses group subexpressions. An operator, such as * or ? works on a single element or on a regular expression enclosed in parentheses.

An AS-path operator is one of the following:

aspath_term {m,n}

A regular expression followed by {m,n} (where m and n are both non-negative integers and m <= n) means at least m and at most n repetitions.

aspath_term {m}

A regular expression followed by {m} (where m is a positive integer) means exactly m repetitions.

aspath_term {m,}

A regular expression followed by {m,} (where m is a positive integer) means m or more repetitions.

aspath_term *

An AS path term followed by * means zero or more repetitions. This is shorthand for {0,}.

aspath_term +

A regular expression followed by + means one or more repetitions. This is shorthand for {1,}.

aspath_term ?

A regular expression followed by ? means zero or one repetition. This is shorthand for {0,1}.

aspath_term aspath_term

Matches the AS term on the left, or the AS term on the right.

For example:

(4250 .*)	Means anything beginning with 4250.
(.* 6301 .*)	Means anything with 6301.
(.* 4250)	Means anything ending with 4250.

(. * 1104112518881135 .*)

Means anything containing 1104 or 1125 or 1888 or 1135.

AS-path regular expressions are used as one of the parameters for determining which routes are accepted and which routes are advertised.

132 SmartSwitch Router User Reference Manual