internetwork
A group of networks that are connected by routers or other connectivity devices so that the networks
function as one network.
Internetwork Operating System (IOS)
Cisco’s proprietary operating system, used in its routers and switches.
Internetwork Packet Exchange (IPX)
The Network−layer protocol generally used by Novell’s NetWare network operating system. IPX
provides connectionless communication, supporting packet sizes up to 64K.
Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX)
Default protocol used in NetWare networks. It is a combination of the IPX protocol to provide
addressing and SPX to provide guaranteed delivery. IPX/SPX is similar to its counterpart, TCP/IP.
Inter−Switch Link (ISL)
A special Cisco proprietary Ethernet protocol that assigns a 26−byte header to an encapsulated frame
and a 4−byte checksum, sometimes referred to as the FCS or the CRC. This protocol is used to send
more than one VLAN between Cisco network devices configured for trunk links.
IPSec A protocol designed for virtual private networks (VPNs). It’s used to provide strong security
standards for encryption and authentication.
IPX address
The unique address used to identify a node in the network.
K−L
kilobit (Kb)
One thousand bits.
kilobyte (K)
One thousand bytes (transmission rate).
LAN Emulation (LANE)
A standard created by the ATM forum to govern the connections of ATM end stations to either
Ethernet or Token Ring devices. LANE provides a bridge from devices using ATM to Layer 2
devices using Ethernet and Token Ring.
LAN Module ASIC (LMA)
An ASIC in the Cisco Catalyst 3000 series switch that provides frame buffering, address learning, bus
arbitration, and switching decisions for Ethernet ports.
latency The time used to forward a packet in and out of a device. This term is commonly used in reference to
routing and switching.
Layer 2 Forwarding Protocol (L2F)
A dial−up VPN protocol designed to work in conjunction with PPP to support authentication
standards, such as TACACS+ and RADIUS, for secure transmissions over the Internet.
Layer 2 Tunneling Protocol (L2TP)
A dial−up VPN protocol that defines its own tunneling protocol and works with the advanced security
methods of IPSec. L2TP allows PPP sessions to be tunneled across an arbitrary medium to a home
gateway at an ISP or corporation.
learning bridge
A bridge that builds its own bridging address table, rather than requiring you to enter information
manually.
Line Module Communication Processor (LCP)
Provides communications for the MCP located on the Supervisor Engine. The LCP is located on each
line module.
local area network (LAN)
A group of connected computers that are located in a geographic area, usually a building or campus,
and that share data and services.
local broadcast
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