Users Guide

advertises itself to another BGP speaker outside its local AS. It can also be set when advertising routes within

an AS. The Next Hop attribute also serves as a way to direct traffic to another BGP speaker, rather than waiting

for a speaker to advertise.

Dell Networking OS allows you to set the Next Hop attribute in the CLI. Setting the Next Hop attribute lets

you determine a router as the next hop for a BGP neighbor.

Multiprotocol BGP

Multiprotocol extensions for BGP (MBGP) are defined in IETF RFC 2858. MBGP allows different types of

address families to be distributed in parallel.

MBGP allows information about the topology of the IP multicast-capable routers to be exchanged separately

from the topology of normal IPv4 and IPv6 unicast routers. It allows a multicast routing topology different

from the unicast routing topology.

NOTE: It is possible to configure BGP peers that exchange both unicast and multicast network layer

reachability information (NLRI), but you cannot connect multiprotocol BGP with BGP. Therefore, you

cannot redistribute multiprotocol BGP routes into BGP.

Implement BGP with Dell Networking

The following sections describe how to implement BGP on Dell Networking OS.

Additional Path (Add-Path) Support

The Add-path feature reduces convergence times by advertising multiple paths to its peers for the same

address prefix without replacing existing paths with new ones. By default, a BGP speaker advertises only the

best path to its peers for a given address prefix. If the best path becomes unavailable, the BGP speaker

withdraws its path from its local RIB and recalculates a new best path. This requires both IGP and BGP

convergence and can therefore be a lengthy process.

BGP add-path on Dell Networking OS reduces the time taken for BGP convergence by advertising multiple

paths to its peers for the same address prefix without new paths implicitly replacing the existing paths. An

iBGP speaker that receives multiple paths from its peers should calculate the best path in its own. BGP add-

path helps switchover to next new best path based on IGP convergence time when best path becomes

unavailable.

Border Gateway Protocol IPv4 (BGPv4) 216