Routers
serve several functions. However, they are used primarily for these
three things:
- Connecting
LANs or networks of different media types
- Filtering broadcasts
and multicasts from servers and other devices
- Providing firewalls
for network security
Because routers
use Layer 3
addresses, which typically have structure, routers can use techniques
(such as address summarization) to build networks that maintain performance
and responsiveness as they grow in size. By imposing structure (usually
hierarchical) on a network, routers can effectively use redundant
paths and determine optimal routes even in a dynamically changing
network.
Switches segment
off collision domains while routers create broadcast domains. Novell
servers will broadcast out their services and network printers will
send out broadcasts telling of their address, etc. Understand that
switch segmenting will not block broadcasts. The more broadcast packets
on a network, the slower the network. Here is
an illustration of collision and broadcast domains.
