Figure 3-2 IGP Versus EGP
Within an autonomous system, most IGP routing can be further classi?¬?ed as conforming to one of
the following algorithms:
?– Distance vector: The distance vector routing approach determines the direction (vector) and
distance (such as hops) to any link in the internetwork.
?– Link-state: The link-state approach, which utilizes the shortest path ?¬?rst (SPF) algorithm,
creates an abstraction of the exact topology of the entire internetwork, or at least of the
partition in which the router is situated.
?– Advanced distance vector: The advanced distance vector approach combines aspects of the
link-state and distance vector algorithms. This is also sometimes referred to as a hybrid
routing protocol.
There is no single best routing algorithm for all internetworks. All routing protocols provide the
information differently.
NOTE The Internet Assigned Numbers Authority (IANA) assigns autonomous system
numbers for many jurisdictions. Use of IANA numbering is required if your organization plans
to use BGP. However, it is good practice to be aware of private versus public autonomous system
numbering schema.
IGPs:
(RIPv2, EIGRP, OSPF)
Autonomous System 50100 Autonomous System 50200
EGPs
(BGP)
Reviewing Dynamic Routing 101
Multiple routes to a destination can exist.
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