User Guide

106 Chapter : AS Path Regular Expressions
Router User Guide
AS Path Terms
A term is one of the following:
AS Matches the given number, which is any positive 16-bit number from 0-65535 inclusive. Note
that valid AS numbers range from one through 65534 inclusive.
!AS Matches any AS number except the given one.
AS1 -AS2 Is a range of ASs. It matches all AS numbers between AS1 and AS2 inclusive.
!AS1 - AS2 This matches all numbers except the given one.
. Matches any number.
null Matches an empty (0 length) string, e.g., (AS1 empty AS2) is equivalent to (AS1 AS2).
term {m, n} A term 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.
term {m} A term followed by {m} (where m is a positive integer) matches m or more repetitions of term.
term {m,} A term followed by {m,} (where m is a positive integer) matches m or more repetitions of term
term * A term followed by * matches zero or more repetitions of term. This is shorthand for {0,}.
term + A term followed by + matches one or more repetitions of term. This is shorthand for {1,}.
term ? A term followed by ? matches zero or one repetition of term. This is shorthand for {0,1}.
[ as_range_list ] Brackets union the items of an as_range_list. An item of this list can be either an AS or a range.
For example, {AS1 AS2 - AS3 AS4] is equivalent to (AS1 | AS2-AS3 | AS4).
( regex ) Parentheses group expressions to make a term out of any regex. An operator, such as * or ?,
works on a regular expression enclosed in parentheses as it would any term.