Alcatel 060320-10, Rev. B Configuration Manual page 98

BGP Overview
•
It makes writing (and reading) policies much easier.
•
It enables the router to begin using the policies more quickly after startup.
For example, to identify routes originating from internal autonomous systems, you would use the pattern:
[64512-65535]$
which means "match any AS number from 64512 to 65535 (inclusive) which occurs at the end of the AS
path." To accomplish the same thing using character-based pattern matching, you would have to use the
following pattern:
(_6451[2-9]_|_645[2-9][0-9]_|_64[6-9][0-9][0-9]_|_65[0-9][0-9][0-9]_)$
Some examples of valid regular expressions are shown in the following table:
Example
100 Meaning:
Matches:
Doesn't Match:
^100 Meaning:
Matches:
Doesn't Match:
100$ Meaning:
Matches:
Doesn't Match:
^100 500$ Meaning:
Matches:
Doesn't Match:
100 . . 200 Meaning:
Matches:
Doesn't Match:
(100|200).+ Meaning:
[500-650]$
page 3-14
Description
Any route which passes through AS number 100.
100 200 300
300 100 100
200 300
Any routes for which the next hop is AS number 100.
100 200 100
50 100 200
Any route which originated from AS number 100 (AS numbers are
prepended to the AS path list as they are passed on, so the originat-
ing AS is always the last number in the list).
100
200 200 100
100 200
A route with just two hops, 100 and 500.
100 500
100 500 600
100 200 500
Any route with at least 4 hops, with 100 separated by any two hops
from 200.
50 100 400 500 200 600
100 100 100 200
100 200
100 100 200
Any route which begins with 100 or 200, ends with an AS number
between 500 and 650 (inclusive), and is at least three hops in length.
The ".+" part matches at least one (but possibly more) AS numbers.
OmniSwitch AOS Release 7 Advanced Routing Configuration Guide
Configuring BGP
March 2011