hello timer: An STP timer that dicates how often the root bridge or switch sends STP hello messages.It also dicates how often nonroot bridges and switches should expect to hear these hello messages.This term may also refer to the Hello timer used by OSPF,which defines how often a router sends OSPF Hello messages.
Hello: A protocol used by OSPF systems to establish and maintain neighbor relationship.Can also refer to the STP Hello BPDU message generates by the root bridge in a Spanning Tree.
holddown: A state into which a route is placed so that routers neither advertise the route nor accept advertisements about it for a specific length of time (the hold-down period).Holddown is used to flush bad information about a route from all routers in the network.A route typically is placed in holddown when a link in that route fails.
IGRP: Interior Gateway Routing Protocol.An Interior Gateway Protocol (IGP) developed by Cisco to address the issues associated with routing in large ,heterogeneous networks.
ISDN: Integrated Services Digital network.A communication protocol offered by telephone companies that permits telephone networks to carry data,voice,and other source traffic.
ISL: inter-Switch link.A Cisco-proprietary protocol that maintains VLAN information as traffic flows between switches and routers.
LAPF: Link Access Procedure Frame Bearer Services.defines the basic Frame relay header and trailer.The header includes DLCI<FECN<BECN<and DE bits.
learn: Transparent bridges and switches learn MAC addresses by examining the source MAC addresses to frame they receive.They add each new MAC address ,along with the port number of the port on which it learned of the MAC address,to an address table.
leased line: A transmission line reserved by a communications carrier for customer’s private use.A leased line is a type of dedicated line.
link-state: A type of routing protocol which sends full topology information about the network to all routers,so they all have a consistent view of the network topology and status.link-state algorithms create a consistent view of the network and therefore are not prone to routing loops.however,they achieve this at the cost of relatively greater computational difficulty and more-widespread traffic (compared with distance vector routing algorithms).