Dell S4820T, Configuration Manual

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waiting for a speaker to advertise. When a next-hop BGP neighbor is unreachable, then the connection to
that BGP neighbor goes down after hold down timer expiry. The connection flap can also be obtained
immediately with Fallover enabled. BGP routes that contain the next-hop as the neighbor address are not
sent to the neighbor. You can enable this feature using the
neighbor sender-side-loopdetect
command.
NOTE: For EBGP neighbors, the next-hop address corresponding to a BGP route is not resolved if
the next-hop address is not the same as the neighbor IP address.
NOTE: The connection between a router and its next-hop BGP neighbor terminates immediately
only if the router has received routes from the BGP neighbor in the past.
Multiprotocol BGP
Multiprotocol extensions for BGP (MBGP) is 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.
MBGP uses either an IPv4 address configured on the interface (which is used to establish the IPv6
session) or a stable IPv4 address that is available in the box as the next-hop address. As a result, while
advertising an IPv6 network, exchange of IPv4 routes does not lead to martian next-hop message logs.
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 OS
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 situation requires both IGP
and BGP convergence and can be a lengthy process. BGP add-path also helps switchover to the next
new best path when the current best path is unavailable.
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Border Gateway Protocol IPv4 (BGPv4)