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Overview
DVMRP
DVMRP (Distance Vector Multicast Routing Protocol) is a multicast routing
protocol (RIP, OSPF, and IGRP are unicast routing protocols). Multicasting is
typically used for real-time audio and video when there is a single source of
data and multiple receivers. DVMRP uses a hop-based metric and, like RIP, a
distance-vector route calculation.
BGP
BGP (Border Gateway Protocol) is an exterior gateway protocol that is used
to exchange network reachability information between BGP-speaking
systems running in each AS. BGP is unlike interior gateway protocols (IGRP
or OSPF), which periodically flood an intra-domain network with all the
known routing table entries and build their own reliability on top of a
datagram service. Instead, BGP uses TCP as its underlying transport
mechanism.
BGP is also a path-vector routing protocol, which limits the distribution of a
firewall's reachability information to its peer or neighbor firewalls. BGP uses
path attributes to provide more information about each route. BGP maintains
an AS path, which includes the number of each AS that the route has
transited. Path attributes may also be used to distinguish between groups of
routes to determine administrative preferences. This allows greater flexibility
in determining route preference and achieves a variety of administrative ends.
BGP supports two basic types of sessions between neighbors: internal (IBGP)
and external (EBGP). Internal sessions run between firewalls in the same
autonomous systems, while external sessions run between firewalls in
different autonomous systems.
Aggregate Routes
Route aggregation allows you to take many small routes and aggregate them
into one large route. This reduces the number of routes advertised for a given
protocol. These aggregate routes are then redistributed into other protocols.
The aggregates are activated by contributing routes. For example, if a firewall
has many stub interface routes subnetted from a class C and is running RIPv2
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Voyager Reference Guide
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