Bgp As Path Filtering Example - Nokia Voyager Reference Manual

6
Configuring Routing

BGP AS Path Filtering Example

BGP updates are used to restrict the routes a router learns or advertises. These
updates can be filtered based on ASPATH regular expressions, neighbors (AS
numbers), or community IDs.
To filter BGP updates based on ASPATH regular expressions, go to
"Configuring Route Inbound Policy on Nokia Platform D Based on ASPATH
Regular Expressions"
detailed description of how to create ASPATH regular expressions.
ASPATH Regular Expressions
1. To accept routes that transit through AS 3662, enter this ASPATH regular
expression in the ASPATH R
(.* 3662 .*)
Select
2. To accept routes whose last autonomous system is 3662, enter this
ASPATH regular expression in the ASPATH R
edit box:
(.* 3662)
Select
3. To accept routes that originated from 2041 and whose last autonomous
system is 701, enter this ASPATH regular expression in the ASPATH
R
2041 701
Select
4. To accept SPRINT (AS number 1239) routes that transit through AT&T
(AS number 7018) or InternetMCI (AS number 3561), enter this ASPATH
regular expression in the ASPATH R
(1239 .* 7018 .*) | (1239 .* 3561 .*)
Select
338
. The following examples, however, give a more
from the O
ANY
from the O
ANY
E
EGULAR XPRESSION
from the O
ANY
from the O
RIGIN
ANY
E
EGULAR XPRESSION
pulldown window; then click A
RIGIN
drop-down window; then click A
RIGIN
edit box:
drop-down window; then click A
RIGIN
EGULAR
drop-down window; then click A
edit box:
.
PPLY
E
EGULAR XPRESSION
.
PPLY
.
PPLY
E
edit box:
XPRESSION
.
PPLY
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