Chapter 10 Dynamic Routing Protocols

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.

Dynamic routing occurs when routers talk to adjacent routers, informing each other of what networks each router is currently connected to .

Unix systems often run the routing daemon named routed.It is provided with almost every implementation of TCP/IP

This section provides an overview of RIP , because it is the most widely used routing protocol.

Normal Operation

Metrics

Problems

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

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.

BGP is an exterior gateway protocol for communication between routers in different autonomous systems.

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.