Cabletron Systems SmartSwitch Router User's Reference Manual page 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 .*)
(.* 6301 .*) Means anything with 6301.
(.* 4250)
(. * 1104|1125|1888|1135 .*)
AS-path regular expressions are used as one of the parameters for determining which
routes are accepted and which routes are advertised.
132
Means anything beginning with 4250.
Means anything ending with 4250.
Means anything containing 1104 or 1125 or 1888 or 1135.
SmartSwitch Router User Reference Manual