4ROUTING WITH IP
This chapter gives an overview of IP routing, specifically defining:
■What IP routing involves
■What elements are necessary for IP routers to effectively transmit packets
■How IP routing transmission errors are detected and resolved
IP Routing and
the OSI Model
An IP router, unlike a bridge, operates at the network layer of the OSI
Reference Model. This means that it routes packets by examining the
network layer address (IP address). Bridges use the data-link layer MAC
addresses to make forwarding decisions. See Figure 4-1.
Figure 4-1 OSI Reference Model and IP Routing
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data-link Layer
Physical Layer
MAC
IP
OSI Reference Model
ARP
RIP
ICMP