
Exterior Gateway Protocols (BGP and EGP)
308628-15.0 Rev 00
1-5
Nortel Networks supports BGP-3 and BGP-4:
• BGP-3 assumes that each advertised network is a natural class network (A, B,
or C), based on its high-order bits. BGP-3 cannot advertise subnets or
supernets.
• BGP-4 has no concept of address classes. Each network listed in the network
layer reachability information (NLRI) portion of an update message contains
a prefix length field, which describes the length of the mask associated with
the network. The prefix length field allows for both supernet and subnet
advertisement. The supernet advertisement is what makes classless
interdomain routing (CIDR) possible. See “Classless Interdomain Routing”
on page 1-4.
In addition, BGP-4 supports BGP confederations and TCP MD5 message
authentication.
This section covers the following topics:
Peer-to-Peer Sessions
A BGP router employs a BGP speaker, which is an entity within the router that
transmits and receives BGP messages and acts upon them. A BGP speaker forms
a neighbor relationship with another BGP speaker by establishing a peer-to-peer
session. See Chapter 4, “
Configuring BGP Peers.”
Topic Page
Peer-to-Peer Sessions 1-5
Stub and Multihomed Autonomous Systems 1-6
Interior BGP Routing 1-6
IBGP Route Reflector 1-7
Equal-Cost Multipath 1-8
BGP Updates 1-8
Path Attributes 1-9
BGP/OSPF Interaction 1-10
BGP-4 Confederations 1-11
BGP-4 TCP MD5 Message Authentication 1-11
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