D

data-driven label assignment.

Assigning labels based on data traffic.

data link layer.

A layer in the OSI model that is responsible for determining the way physical media will be accessed and the way data is formatted.

default network.

A network that is designated as the default; a router will send all packets to destinations for which it has no specific route to the default network; used only in EIGRP and IGRP.

default route.

A route that matches all IP addresses (0.0.0.0) but has a short prefix length (0); this is the route that the router will use when it has no more specific information on how to reach a given destination.

DeMilitarized Zone.

See [DMZ. DeMilitarized Zone. A buffer between a dirty, or untrusted, network and the clean, or trusted, area of the network.]

designated router.

See [DR. designated router. An OSPF router that is responsible for flooding routing information onto a broadcast link and advertising reachability to the link.]

directed broadcast.

A packet that is destined to the broadcast address of another segment; for example, 10.1.1.255 is the directed broadcast address of the 10.1.1.0/24 segment.

discontiguous network.

A network address that is used in several different areas of a network, which are not connected; generally, this refers to a major network, but it could refer to virtually any unit of addressing.

distance vector.

A routing protocol in which each router advertises all reachable destinations known to directly connected neighbors; EIGRP is an advanced distance vector protocol. Other distance vector protocols are IGRP and RIP.

distribution.

The area or layer of the network that is responsible for traffic aggregation and route summarization.

distribution list.

Used to block the advertisement of given destinations by a routing protocol.

DMZ. DeMilitarized Zone.

A buffer between a dirty, or untrusted, network and the clean, or trusted, area of the network.

DR. designated router.

An OSPF router that is responsible for flooding routing information onto a broadcast link and advertising reachability to the link.

dual-homed.

Attaching one device to two places in the next layer of the network.