Administrator Guide

Configuring IP Community Lists
Mmultiple methods of manipulating routing attributes are supported in the Dell Networking OS.
One attribute you can manipulate is the COMMUNITY attribute. This attribute is an optional attribute that is defined for a group
of destinations. You can assign a COMMUNITY attribute to BGP routers by using an IP community list. After you create an IP
community list, you can apply routing decisions to all routers meeting the criteria in the IP community list.
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.
The system 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.
Dell#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
deny 14551:666
Dell#
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Border Gateway Protocol IPv4 (BGPv4)