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Glossary
FDDI
Fiber Distributed Data Interface: A LAN standard, defined by ANSI
X3T9.5 that can run at speeds up to 200Mbps and uses token-passing media
access on fiber-optic cable. For redundancy, FDDI can use a dual-ring
architecture.
feasible successor
A route that is kept in a topology table and will be
placed in the routing table if the current successor goes down.
FECN
Forward Explicit Congestion Notification: A bit set by a Frame
Relay network that informs the DTE receptor that congestion was encoun-
tered along the path from source to destination. A device receiving frames
with the FECN bit set can ask higher-priority protocols to take flow-control
action as needed. See also: BECN.
FEIP
Fast Ethernet Interface Processor: An interface processor employed
on Cisco 7000 series routers, supporting up to two 100Mbps 100BaseT
ports.
firewall
A barrier purposefully erected between any connected public net-
works and a private network, made up of a router or access server or several
routers or access servers, that uses access lists and other methods to ensure
the security of the private network.
Flash
Electronically Erasable Programmable Read-Only Memory
(EEPROM). Used to hold the Cisco IOS in a router by default.
flash memory
Developed by Intel and licensed to other semiconductor
manufacturers, it is nonvolatile storage that can be erased electronically and
reprogrammed, physically located on an EEPROM chip. Flash memory per-
mits software images to be stored, booted, and rewritten as needed. Cisco
routers and switches use flash memory to hold the IOS by default. See also:
EPROM and EEPROM.
flat network
Network that is one large collision domain and one large
broadcast domain.
flooding
When traffic is received on an interface, it is then transmitted to
every interface connected to that device with the exception of the interface
from which the traffic originated. This technique can be used for traffic
transfer by bridges and switches throughout the network.
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