Policy Framework Configuration Guide - Juniper Networks

Junos 10.4 Policy Framework Configuration Guide
Table 16: Examples of AS Path Regular Expressions (continued)
AS Path to Match
Regular
Expression
Sample Matches
Path of any length, except nonexistent, whose
second AS number can be anything, including
nonexistent
. .* or . .{0,}
12341234567812345678
AS path is 1 2 3
1 2 3
1 2 3
One occurrence of the AS numbers 1 and 2, followed
by one or more occurrences of the AS number 3
1 2 3+
1 2 3
1 2 3 3
1 2 3 3 3
One or more occurrences of AS number 1, followed
by one or more occurrences of AS number 2, followed
by one or more occurrences of AS
number 3
1+ 2+ 3+
1 2 3
1 1 2 3
1 1 2 2 3
1 1 2 2 3 3
Path of any length that begins with AS numbers 4,
5, 6
4 5 6 .*
4 5 6
4 5 6 7 8 9
Path of any length that ends with AS numbers 4, 5, 6
.* 4 5 6
4 5 6
1 2 3 4 5 6
4 9 4 5 6
AS path 5, 12, or 18
5 | 12 | 18
5
12
18
Configuring a Null AS Path
You can use AS path regular expressions to create a null AS path that matches routes
(prefixes) that have originated in your AS. These routes have not been advertised to your
AS by any external peers. To create a null AS path, use the parentheses operator enclosed
in quotation marks with no intervening spaces:
“()"
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