domain. As you might have guessed, hubs only allow one device per network
to communicate at a time.
into a switch port and then connect multiple Ethernet hosts into the hub, but
you can't mix Token Ring hosts in with the Ethernet gang on the same seg-
ment. Mixing hosts in this manner is called media translation, and Cisco says
you've just got to have a router around if you need to provide this service.
things: It sends bits and receives bits. Bits come only in values of 1 or 0--a
Morse code with numerical values. The Physical layer communicates directly
with the various types of actual communication media. Different kinds of
media represent these bit values in different ways. Some use audio tones,
while others employ state transitions--changes in voltage from high to low
and low to high. Specific protocols are needed for each type of media to
describe the proper bit patterns to be used, how data is encoded into media
signals, and the various qualities of the physical media's attachment
interface.
physical link between end systems. This layer is also where you identify the
interface between the data terminal equipment (DTE) and the data commu-
nication equipment (DCE). The DCE is usually located at the service pro-
vider, while the DTE is the attached device. The services available to the DTE
are most often accessed via a modem or channel service unit/data service unit
(CSU/DSU).
The CCNA exam is only interested in the Ethernet standards.
and reamplifies or regenerates that signal, and then forwards the digital sig-
nal out all active ports without looking at any data. An active hub does the
same thing. Any digital signal received from a segment on a hub port is