User guide

Chapter 1. Router Concepts 15
Chapter 1. Router Concepts
This chapter provides background information applicable to the router on topics useful to network administrators.
These topics include:
¥ Routing and bridging
¥ Routing and bridging controls
¥ Bridge filtering
¥ Voice routing
¥ PAP/CHAP security authentication
¥ Security passwords and levels
¥ Interoperability between the router and other systems
¥ Protocol conformance
¥ Encapsulation options
¥ System files
Routing and Bridging
The router can operate as a bridge, a router, or as both (sometimes called a brouter). The following sections
describe routing and bridging and how the two functions operate together.
Routing
Routing is the process that determines where data is sent. A router can route user data from source to destination
over different LAN and WAN links. Routing relies on routing address tables to determine the best path for each
packet to take.
The routes within a routing address table are established in two ways:
¥ The routing tables can be seeded, that is, addresses for remote destinations are placed in the table along with
path details and the associated costs (path latency).
¥ The routing tables can also be built dynamically; i.e., the location of remote stations, hosts, and networks are
updated from broadcast packet information.
Routing helps to increase network capacity by localizing traffic on LAN segments. It also provides security by
isolating traffic on segmented LANs. Routing extends the reach of networks beyond the limits of each LAN
segment.