Reference Guide

156 | Border Gateway Protocol
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Figure 8-26. Command example: show ip bgp paths
AS-PATH ACLs use regular expressions to search AS_PATH values. AS-PATH ACLs have an “implicit
deny.” This means that routes that do not meet a deny or match filter are dropped.
Use these commands in the following sequence, starting in the CONFIGURATION mode to configure an
AS-PATH ACL to filter a specific AS_PATH value.
Step Command Syntax Command Mode Purpose
1
ip as-path access-list
as-path-name
CONFIGURATION Assign a name to a AS-PATH ACL and enter AS-PATH
ACL mode.
2
{deny | permit} filter
parameter
CONFIG-AS-PATH Enter the parameter to match BGP AS-PATH for
filtering. This is the filter that will be used to match the
AS-path. The entries can be any format, letters,
numbers, or regular expressions.
This command can be entered multiple times if multiple
filters are desired.
Refer to Table 8-4 for accepted expressions.
3
exit AS-PATH ACL Return to CONFIGURATION mode
4
router bgp as-number CONFIGURATION Enter ROUTER BGP mode.
5 neighbor {ip-address |
peer-group-name}
filter-list as-path-name
{
in | out}
CONFIG-ROUTER-B
GP
Use a configured AS-PATH ACL for route filtering and
manipulation.
If you assign an non-existent or empty AS-PATH ACL,
the software allows all routes.
FTOS#show ip bgp paths
Total 30655 Paths
Address Hash Refcount Metric Path
0x4014154 0 3 18508 701 3549 19421 i
0x4013914 0 3 18508 701 7018 14990 i
0x5166d6c 0 3 18508 209 4637 1221 9249 9249 i
0x5e62df4 0 2 18508 701 17302 i
0x3a1814c 0 26 18508 209 22291 i
0x567ea9c 0 75 18508 209 3356 2529 i
0x6cc1294 0 2 18508 209 1239 19265 i
0x6cc18d4 0 1 18508 701 2914 4713 17935 i
0x5982e44 0 162 18508 209 i
0x67d4a14 0 2 18508 701 19878 ?
0x559972c 0 31 18508 209 18756 i
0x59cd3b4 0 2 18508 209 7018 15227 i
0x7128114 0 10 18508 209 3356 13845 i
0x536a914 0 3 18508 209 701 6347 7781 i