Planet Networking & Communication CS-2001 User Manual page 42

Note：
Dynamic Routing Protocols can be categoried into the following two categories:
1.

Distance-Vector Routing Protocol: Uses the Bellman-Ford algorithm to
calculate paths. Examples of distance-vector routing protocols include
RIPv1/2 and IGRP (Cisco's proprietary protocol). Using RIP, the maximum
hop count from the first router to the destination is 15. Any destination greater
than 15 hops away is considered unreachable. A distance-vector routing
protocol requires that a router informs its neighbors of topology changes
periodically and, in some cases, when a change is detected in the topology of a
network. Its suitable for networks containing fewer than 100 hops (routers), or
small networks that are not changed frequently.

Link state routing protocols use the Dijkstra algorthim to calculate the Shortest
Path First (SPF) address some of the limitations of distance vector routing
protocols. For example, link state routing protocols provide faster convergence
than do distance vector routing protocols and have no limit to the amount of
hops. VLSM and CIDR are also supported. Although link state routing
protocols are more reliable and require less bandwidth than do distance vector
routing protocols, they are also more complex, more memory-intensive, and
place a greater load on the CPU.
Dynamic routing protocols depend on the location of the router in the Autonomous
2.
Sytstem (AS). There are two classifications:

IGP - Interior Gateway Protocol: Examples include: RIP, IGRP, EIGRP, OSPF
and IS-IS are interior gateway protocols.

EGP - Exterior Gateway Protocol: Uses a simple tree topology, but posses
some shortcomings that the Border Gateway Protocol (BGP) has fixed.
Within the Internet, an autonomous system (AS) is a collection of connected
3.
Internet Protocol (IP) routing prefixes under the control of one or more network
operators that presents a common, clearly defined routing policy to the Internet.
Multiple organizations can run BGP using private AS numbers to an ISP that
connects all those organizations to the Internet. Even though there are multiple
Autonomous Systems supported by the ISP, the Internet only sees the routing
policy of the ISP. That ISP must have an officially registered Autonomous System
Number (ASN). A unique ASN is allocated to each AS for use in BGP routing. AS
numbers are important because the ASN uniquely identifies each network on the
Internet.

Until 2007, AS numbers were defined as 16-bit integers, which allowed for a
maximum of 65536 assignments. The Internet Assigned Numbers Authority
(IANA) has designated ASN numbers 64512 through 65534 to be used for
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