Concept Guide

Enabling Additional Paths
The additional path allows the advertisement of more paths in addition to the best path. Enabling additional path allows the advertisement
of multiple paths for the same address prex without the new paths replacing any previous paths. The additional path feature is disabled by
default.
NOTE: Dell EMC Networking OS recommends not to use 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 (send, receive or both).
CONFIG-ROUTER-BGP or CONFIG-ROUTER-BGP-AF mode
bgp add-path [send | received | both] path-count
Congure the following parameters:
• send: Indicate that the system sends multiple paths to peers.
• received: Indicate that the system accepts multiple paths from peers.
• both: Indicate that the system sends and accepts multiple paths from peers.
• path-count: Indicate that the system sends multiple paths to peers. The range is from 2 to 64.
2 Allow the specied neighbor or peer group to allow multiple path advertisements.
CONFIG-ROUTER-BGP or CONFIG-ROUTER-BGP-AF mode
neighbor [ip-address | ipv6–address | peer-group-name] add-path [send | received | both]
path-count
NOTE
: The path-count parameter controls the number of paths that are advertised, not the number of paths that are
received.
Example conguration for enabling additional paths
DellEMC# configure terminal
DellEMC(conf)# router bgp 400
DellEMC(conf-router_bgp)# neighbor 10.10.10.1 remote-as 500
DellEMC(conf-router_bgp)# bgp add-path both 2
DellEMC(conf-router_bgp)# address-family ipv4 multicast
DellEMC(conf-router_bgp_af)# neighbor 10.10.10.1 activate
DellEMC(conf-router_bgp_af)# neighbor 10.10.10.1 add-path both 3
DellEMC(conf-router_bgp_af)# exit
The above conguration example shows how to enable BGP additional paths to be sent and received with a maximum of two additional
paths to the peers. You can congure the neighbor to send and receive additional paths using the neighbor add-pathcommand at the
address family conguration level.
Conguring IP Community Lists
Within Dell EMC 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 EMC 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:
Border Gateway Protocol (BGP)
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