Administrator Guide

Enabling Additional Paths
The add-path feature is disabled by default.
NOTE: Dell Networking OS recommends not using multipath and add path simultaneously in a route reector.
To allow multiple paths sent to peers, use the following commands.
1 Allow the advertisement of multiple paths for the same address prex without the new paths replacing any previous ones.
CONFIG-ROUTER-BGP mode
bgp add-path [both|received|send] path-count count
The range is from 2 to 64.
2 Allow the specied neighbor/peer group to send/ receive multiple path advertisements.
CONFIG-ROUTER-BGP mode
neighbor add-path
NOTE: The path-count parameter controls the number of paths that are advertised, not the number of paths that are
received.
Conguring IP Community Lists
Within Dell Networking OS, you have multiple methods of manipulating routing attributes.
One attribute you can manipulate is the COMMUNITY attribute. This attribute is an optional attribute that is dened for a group of
destinations. In Dell Networking OS, 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 denes the COMMUNITY attribute and the predened 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 dened 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.
Dell Networking OS also supports BGP Extended Communities as described in RFC 4360 — BGP Extended Communities Attribute.
To congure 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 Congure a community list by denying or permitting specic 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 specic to that
autonomous system.
Border Gateway Protocol IPv4 (BGPv4)
201