Reference Guide

IETF RFC 1997 defines the COMMUNITY attribute and the predefined communities of INTERNET,
NO_EXPORT_SUBCONFED, NO_ADVERTISE, and NO_EXPORT. All BGP routes belong to the INTERNET community. In
the RFC, the other communities are defined as follows:
• All routes with the NO_EXPORT_SUBCONFED (0xFFFFFF03) community attribute are not sent to CONFED-EBGP
or EBGP peers, but are sent to IBGP peers within CONFED-SUB-AS.
• All routes with the NO_ADVERTISE (0xFFFFFF02) community attribute must not be advertised.
• All routes with the NO_EXPORT (0xFFFFFF01) community attribute must not be advertised outside a BGP
confederation boundary, but are sent to CONFED-EBGP and IBGP peers.
FTOS also supports BGP Extended Communities as described in RFC 4360 — BGP Extended Communities Attribute.
To configure an IP community list, use these commands.
1. Create a community list and enter COMMUNITY-LIST mode.
CONFIGURATION mode
ip community-list community-list-name
2. Configure a community list by denying or permitting specific community numbers or types of community.
CONFIG-COMMUNITYLIST mode
{deny | permit} {community-number | local-AS | no-advertise | no-export |
quote-regexp regular-expression-list | regexp regular-expression}
– community-number: use AA:NN format where AA is the AS number (2 Bytes or 4 Bytes) and NN is a
value specific to that autonomous system.
– local-AS: routes with the COMMUNITY attribute of NO_EXPORT_SUBCONFED.
– no-advertise: routes with the COMMUNITY attribute of NO_ADVERTISE.
– no-export: routes with the COMMUNITY attribute of NO_EXPORT.
– quote-regexp: then any number of regular expressions. The software applies all regular expressions in
the list.
– regexp: then a regular expression.
To view the configuration, use the show config command in CONFIGURATION COMMUNITY-LIST or
CONFIGURATION EXTCOMMUNITY LIST mode or the show ip {community-lists | extcommunity-
list
} command in EXEC Privilege mode.
Example of the show ip community-lists Command
FTOS#show ip community-lists
ip community-list standard 1
deny 701:20
deny 702:20
deny 703:20
deny 704:20
deny 705:20
deny 14551:20
deny 701:112
deny 702:112
deny 703:112
deny 704:112
deny 705:112
deny 14551:112
deny 701:667
deny 702:667
deny 703:667
deny 704:666
deny 705:666
188