Regular Expressions - Alcatel-Lucent 7705 Configuration Manual

Configuring Route Policies

Regular Expressions

The ability to perform a filter match in the AS-PATH is supported. This feature allows
customers to configure match criteria for specific sequences within the AS path so that they
can be filtered out before cluttering the service provider's routing information base (RIB).
The 7705 SAR OS uses regular expression strings to specify match criteria for:
A regular expression is expressed as a combination of terms and operators. Regular
expressions should always be enclosed in quotes.
Terms
A term for an AS path regular expression is:
A term for a community string regular expression is a string that is evaluated character by
character and is composed of:
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• an AS path string; for example, "100 200 300"
• a community string; for example, "100:200", where 100 is the AS number and 200
is the community-value
• an elementary term; for example, an AS number "200"
• a range term composed of two elementary terms separated by the "-" character, such
as "200-300"
• the "." dot wildcard character, which matches any elementary term
• a regular expression enclosed in parenthesis "( )"
• a regular expression enclosed in square brackets used to specify a set of choices of
elementary or range terms; for example, [100-300 400] matches any AS number
between 100 and 300 or the AS number 400
• an elementary term, which for a community string is any single digit, such as "4"
• a range term composed of two elementary terms separated by the "-" character, such
as "2-3"
• a colon ":" to delimit the AS number from the community value
• the "." dot wildcard character, which matches any elementary term or ":"
• a regular expression enclosed in parenthesis "( )"
• a regular expression enclosed in square brackets, which is used to specify a set of
choices of elementary or range terms; for example, [1-3 7] matches any single digit
between 1 and 3 or the digit 7
7705 SAR OS Router Configuration Guide