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Installation Prerequisites
Microcode Overview
The FEIP microcode (firmware) is an image that provides card-specific software instructions. A
programmable read-only memory (PROM) device on the FEIP contains a default microcode boot
image that assists the system in finding and loading the microcode image from the Cisco IOS
software bundle or Flash memory. The router supports downloadable microcode, which allows you
to upgrade microcode versions by downloading new microcode images, storing them in system
Flash memory, and instructing the system to load its image from Flash. You can store multiple
images for an interface type and, with a configuration command, instruct the system to load any one
of them or the default microcode image. The microcode boot image in the PROM initializes the FEIP
and then assists downloading the FEIP microcode image. All interfaces of the same type (FEIP, and
so on) load the same microcode image, either from the microcode image bundled with the Cisco IOS
software or from an image stored in system Flash. Although multiple microcode versions for a
specific interface type can be stored concurrently in Flash, only one image can load at startup.
The show controllers cbus command displays the currently loaded and running microcode version
for each interface processor, and FEIP. The show startup-config EXEC command shows the current
system instructions for loading microcode at startup.
Software and interface processor microcode images are carefully optimized and bundled to work
together. Overriding the bundle can result in system incompatibilities. We recommend that you use
the microcode included in the software bundle. For a complete description of microcode and
downloading procedures, refer to the section "Upgrading FEIP Microcode" on page 37.
Fast Ethernet Overview
The term Ethernet is commonly used for all carrier sense multiple access/collision detection
(CSMA/CD), local-area networks (LANs) that generally conform to Ethernet specifications,
including Fast Ethernet under IEEE 802.3u.
Note
Environment B.
IEEE 802.3u is well suited to applications where a local communication medium must carry
sporadic, occasionally heavy traffic at high peak data rates. Stations on a CSMA/CD LAN can access
the network at any time. Before sending data, the station listens to the network to see if it is already
in use. If it is, the station waits until the network is not in use, then transmits; this is half-duplex
operation.
A collision occurs when two stations listen for network traffic, hear none, and transmit very close to
simultaneously. When this happens, both transmissions are damaged, and the stations must
retransmit. The stations detect the collision and use backoff algorithms to determine when they
should retransmit. Both Ethernet and IEEE 802.3u are broadcast networks, which means that all
stations see all transmissions. Each station must examine received frames to determine if it is the
intended destination and, if it is, to pass the frame to a higher protocol layer for processing.
IEEE 802.3u specifies the following different physical layers for 100BASE-T:
•
•
8 Fast Ethernet Interface Processor (FEIP) Installation and Configuration
100BASE-TX is intended for Environment A, and 100BASE-FX is intended for
100BASE-TX—100BASE-T, half and full duplex over Category 5 unshielded twisted-pair
(UTP), Electronics Industry Association/Telecommunications Industry Association
[EIA/TIA]-568-compliant cable
100BASE-FX—100BASE-T, half and full duplex over optical fiber
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