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Glossary

helper address

The unicast address specified, which instructs the Cisco

router to change the client's local broadcast request for a service into a
directed unicast to the server.

hierarchical addressing

Any addressing plan employing a logical chain of

commands to determine location. IP addresses are made up of a hierarchy of
network numbers, subnet numbers, and host numbers to direct packets to
the appropriate destination.

hierarchical network

A multi-segment network configuration providing

only one path through intermediate segments between source segments and
destination segments.

hierarchy

See: hierarchical network.

HIP

HSSI Interface Processor: An interface processor used on Cisco 7000

series routers, providing one HSSI port that supports connections to ATM,
SMDS, Frame Relay, or private lines at speeds up to T3 or E3.

hold-down

The state a route is placed in so that routers can neither adver-

tise the route nor accept advertisements about it for a defined time period.
Hold-down is used to surface bad information about a route from all routers
in the network. A route is generally placed in hold-down when one of its
links fails.

hop

The movement of a packet between any two network nodes. See also:

hop count.

hop count

A routing metric that calculates the distance between a

source and a destination. RIP employs hop count as its sole metric.
See also: hop and RIP.

host address

Logical address configured by an administrator or server on

a device. Logically identifies this device on an internetwork.

HSCI

High-Speed Communication Interface: Developed by Cisco, a single-

port interface that provides full-duplex synchronous serial communications
capability at speeds up to 52Mbps.

HSRP

Hot Standby Router Protocol: A protocol that provides high net-

work availability and provides nearly instantaneous hardware fail-over
without administrator intervention. It generates a Hot Standby router
group, including a lead router that lends its services to any packet being
transferred to the Hot Standby address. If the lead router fails, it will be
replaced by any of the other routers--the standby routers--that monitor it.

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