Users Guide

1370 BGP
the adjacency to the unreachable neighbor is no longer ESTABLISHED, and
if an UPDATE is sent to the neighbor's update group, BGP does not try to
send to the failed neighbor. When the failed adjacency is reestablished, BGP
resends all routing information to the neighbor.
Both internal and external fallover should happen within a second of the loss
of reachability. Enabling fast fallover should relax the need to set a short hold
time and send KEEPALIVE messages rapidly.
Authentication
RFC 4271 requires support for TCP MD5 authentication as specified in RFC
2385. Dell EMC Networking supports TCP MD5 authentication. The
network administrator may optionally enable TCP MD5 for a specific peering
session by configuring a password on each end of the connection.
Because of concerns about the increasing vulnerability of MD5, the IETF has
recently obsoleted RFC 2385, replacing it with more robust mechanisms
specified in RFC 5925, The TCP Authentication Option. In spite of this,
support for TCP MD5 has some near-term value: it allows interoperability
with other implementations that do not yet support RFC 5925. Dell EMC
Networking BGP does not support for RFC 5925.
Outbound Update Groups
To reduce the memory required for the Adj-RIB-Out and to reduce the
processing required by the phase 3 decision process, BGP sorts peers into
update groups. Every peer in an update group has the same configured (or
default) value for minRouteAdvertisementInterval and the same set of
outbound policies. Each update group contains only internal or external
peers. Thus, the same information is advertised to every peer in the update
group and may be advertised at the same time. A single advertised path list
(Adj-RIB-Out) is retained for each update group. A single UPDATE message
is constructed and a copy sent to each peer in the update group. When a peer
in the ESTABLISHED state moves from one update group to another
because of a configuration change, BGP withdraws all prefixes previously
advertised to the peer and advertises to the peer the Adj-RIB-Out of the new
update group.
BGP maintains separate update groups for IPv4 and IPv6. If IPv6 is active for
a peer with an IPv4 address, the peer is in both an IPv4 update group and in
an IPv6 update group. A neighbor may be in an IPv6 update group for an IPv4