Fast Ethernet
Rather than crave campuses to advance in a absolutely new technology to accretion increased
bandwidth, the networking industry developed a higher-speed Ethernet based on the existing
Ethernet standards. Fast Ethernet operates at 100 Mbps and is based on the IEEE 802.3u
standard. The Ethernet cabling schemes, CSMA/CD operation, and all upper-layer protocol
operations accept been maintained with Fast Ethernet. The net aftereffect is the aforementioned abstracts articulation Media
Access Control (MAC) band alloyed with a new concrete layer.
In the campus network, Fast Ethernet can be acclimated to articulation admission and administration band switches.
The beyond bandwidth can abutment the accumulated cartage from assorted Ethernet segments in the
access layer. Fast Ethernet can additionally be acclimated to affix administration band switches to the core,
with either distinct or assorted bombastic links. It can additionally be acclimated to affix faster end user
workstations to the admission band switch, and to accommodate bigger connectivity to enterprise
servers. In added words, Fast Ethernet can be auspiciously deployed at all layers aural a campus
network.
Cabling for Fast Ethernet can absorb either UTP or fiber. Specifications for Fast Ethernet define
the media types and distances as apparent in Table 3-2.
72 Chapter 3: Basic About-face and Anchorage Configuration
Full-Duplex Fast Ethernet
As with acceptable Ethernet, the accustomed progression to advance achievement is to use fullduplex
operation. Fast Ethernet can accommodate 100 Mbps in anniversary administration on a switched
connection, for 200 Mbps absolute throughput. This throughput is alone accessible back a
workstation or server is anon affiliated to a about-face port, or back two switches directly
connect to anniversary other.
The Fast Ethernet blueprint additionally offers astern affinity to abutment acceptable 10
Mbps Ethernet. To accommodate this support, two accessories at anniversary end of a arrangement affiliation can
automatically accommodate articulation capabilities so that they both can accomplish at a best common
level. This agreement involves the apprehension and alternative of the accomplished concrete layer
technology (available bandwidth) and half-duplex or full-duplex operation. Even if one of the
devices uses a anchored configuration, the added accessory can ascertain this and bout the capabilities.
Autonegotiation uses the priorities apparent in Table 3-3 for anniversary approach of Ethernet to determine
which technology to accede upon. If both accessories can abutment added than one technology, then
the technology with the accomplished antecedence will be used. For example, if two accessories can support
both 10BaseT and 100BaseTX, both accessories will use the college antecedence 100BaseTX mode.
Table 3-2 Cabling Specifications for Fast Ethernet
Technology Wiring Type Pairs Cable Length
100BaseTX EIA/TIA Category 5 UTP 2 100 m
100BaseT2 EIA/TIA Category 3,4,5 UTP 2 100 m
100BaseT4 EIA/TIA Category 3,4,5 UTP 4 100 m
100BaseFX Multimode cilia (MMF)
62.5 micron core, 125 micron outer
cladding (62.5/125)
1 400 m bisected duplex
or
2000 m abounding duplex
Single-mode cilia (SMF) 1 10 km
Table 3-3 Autonegotiation Alternative Priorities
Priority Ethernet Mode
7 100BaseT2 (full duplex)
6 100BaseT2 (half duplex)
5 100BaseTX (full duplex)
4 100BaseT4
3 100BaseTX
2 10BaseT (full duplex)
1 10BaseT
Desktop Connectivity with Ethernet 73
NOTE To assure able agreement at both ends of a link, Cisco recommends that the appropriate
values for manual acceleration and bifold approach be manually configured on about-face ports.
Cisco provides one added adequacy to Fast Ethernet, which allows several Fast Ethernet
links to be arranged calm for added throughput. Fast EtherChannel (FEC) allows two to
eight full-duplex Fast Ethernet links to act as a distinct concrete link, for 400- to 1600-Mbps
bandwidth. This technology is declared in greater detail in Chapter 5, “Redundant Switch
Links.”
For added account about Fast Ethernet technology, accredit to Cisco’s web site: www.cisco.com/
warp/public/cc/so/neso/lnso/lnmnso/feth_tc.htm