fabric module (FM)

For more information about available fabric modules, see "Fabric Modules" in the ExtremeSwitching X8 Series Switches Hardware Installation Guide.

fast convergence

In EAPS, Fast Convergence allows convergence in the range of 50 milliseconds. This parameter is configured for the entire switch, not by EAPS domain.

fast path

This term refers to the data path for a packet that traverses the switch and does not require processing by the CPU. Fast path packets are handled entirely by ASICs and are forwarded at wire speed rate.


Forwarding database. The switch maintains a database of all MAC address received on all of its ports and uses this information to decide whether a frame should be forwarded or filtered. Each FDB entry consists of the MAC address of the sending device, an identifier for the port on which the frame was received, and an identifier for the VLAN to which the device belongs. Frames destined for devices that are not currently in the FDB are flooded to all members of the VLAN. For some types of entries, you configure the time it takes for the specific entry to age out of the FDB.


Frequency-Hopping Spread Spectrum. A transmission technology used in Local Area Wireless Network (LAWN) transmissions where the data signal is modulated with a narrowband carrier signal that 'hops' in a random but predictable sequence from frequency to frequency as a function of time over a wide band of frequencies. This technique reduces interference. If synchronized properly, a single logical channel is maintained. (Compare with DSSS.)


Forwarding Information Base. On BlackDiamond 8800 series switches and Summit family switches, the Layer 3 routing table is referred to as the FIB.

fit, thin, and fat APs

A thin AP architecture uses two components: an access point that is essentially a stripped-down radio and a centralized management controller that handles the other WLAN system functions. Wired network switches are also required. 

A fit AP, a variation of the thin AP, handles the RF and encryption, while the central management controller, aware of the wireless users' identities and locations, handles secure roaming, quality of service, and user authentication. The central management controller also handles AP configuration and management.

A fat (or thick) AP architecture concentrates all the WLAN intelligence in the access point. The AP handles the radio frequency (RF) communication, as well as authenticating users, encrypting communications, secure roaming, WLAN management, and in some cases, network routing.


This is the unit of transmission at the data link layer. The frame contains the header and trailer information required by the physical medium of transmission.


Fully Qualified Domain Name. A 'friendly' designation of a computer, of the general form computer.[subnetwork.].organization.domain. The FQDN names must be translated into an IP address in order for the resource to be found on a network, usually performed by a DNS.


This is the communication mode in which a device simultaneously sends and receives over the same link, doubling the bandwidth. Thus, a full-duplex 100 Mbps connection has a bandwidth of 200 Mbps, and so forth. A device either automatically adjusts its duplex mode to match that of a connecting device or you can configure the duplex mode; all devices at 1 Gbps or higher run only in full-duplex mode.


Forwarding Table Manager.


File Transfer Protocol.