How AS Path Regular Expressions Are Evaluated

AS path regular expressions implement the extended (modern) regular expressions as defined in POSIX 1003.2. They are identical to the UNIX regular expressions with the following exceptions:

• The basic unit of matching in an AS path regular expression is the AS number and not an individual character.
• A regular expression matches a route only if the AS path in the route exactly matches regular-expression. The equivalent UNIX regular expression is ^regular-expression$. For example, the AS path regular expression 1234 is equivalent to the UNIX regular expression ^1234$.
• You can specify a regular expression using wildcard operators.