10.1 Introduction
Our discussion in the previous chapter dealt with static routing.
this chapter looks at the dynamic routing protocols used by routers to communicate with each other.
10.2 Dynamic Routing
Dynamic routing occurs when routers talk to adjacent routers, informing each other of what networks each router is currently connected to .
10.3 Unix Routing Daemons
Unix systems often run the routing daemon named routed.It is provided with almost every implementation of TCP/IP
10.4 RIP: Routing Information Protocol
This section provides an overview of RIP , because it is the most widely used routing protocol.
Normal Operation
Initialization
Request received
Response received
Regular routing updates
Triggered updates
Metrics
The metrics used by RIP are hop couts. The hop count for all directly connected interfaces is 1.
Problems
As simple as this sounds, there are pitfalls.
10.5 RIP Version 2
these extensions don't change the protocol , but pass additional information in the fields labeled "must be zero" in Figure 10.3 .RIP and RIP-2 can interoperate if RIP ignores the fields that must be zero
10.6 OSPF: Open Shortest Path First
OSPF is a link-state protocol, as opposed to RIP , which is a distance-vector protocol. The term distance-vector means the messages sent by RIP contain a vector of distances . Each router updates its routing table based on the vector of these distance that it receives from its neighbors.
10.7 BGP: Border Gateway Protocol
BGP is an exterior gateway protocol for communication between routers in different autonomous systems.
10.8 CIDR: Classless Interdomain Routing
In chapter 3 we said there is a shortage of Class B addresses, requiring sites with multiple networks to now obtain multiple class C network IDs, instead of a single class B network ID.
