Specifications

Routers
6-6 Ethernet Devices
Unlike a repeater, which sends all frames it receives to all segments it is
connected to, a bridge reads the frames it receives and decides whether to
filter or forward the frame based on the addressing information contained
within it. Bridges can also be used to connect similar networks (networks
with the same upper five layers of the OSI model) such as Ethernet, Token
Ring, and Fiber Distributed Data Interface (FDDI) together. Because
bridges work at layer 2 of the OSI Model, they are protocol independent.
They have a longer response time than repeaters because a bridge must
read the complete data frame, check for errors, and make forward or filter
decisions based on recognized addresses stored in its source address table.
Bridges are discussed further in Chapter 9, Ethernet Bridge Operation.
Routers
A router works much like a bridge, except that a router pays attention to
the upper network layer protocols (OSI model level 3) rather than just
Physical Layer protocols like a bridge. A router will decide whether to
forward a packet by looking at the protocol level addresses rather than the
MAC address. Because routers transfer packets between different media
types, many routers can also function as bridges.
A detailed discussion of routing operations is beyond the scope of this
guide.
The following chapter explains the use of each of these devices while
considering your Ethernet network design.