Cabletron Systems SmartSwitch - Manual (Page 132)

Chapter 10: BGP Configuration Guide
132 SmartSwitch Router User Reference Manual
( 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.
(. * 1104|1125|1888|1135 .*)
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.