CCNA

Description:	CCNA Study Definitions
Category:	Miscellaneous
Created by:	kmusk01 on 2009-01-15

Question	Answer
ARP	Address Resolution Protocol. An Internet protocol used to map an IP address to a MAC address.
Default Gateway/Router	On an IP host, the IP address of some router to which, the host sends packets when the packet's destination address is on a subnet other than the local subnet.
DHCP	Dynamic Host Configuration Protocol. A protocol used by hosts to dynamically discover and lease an IP address, and learn the correct subnet mask, default gateway, and DNS server IP address.
DNS	Domain Name System. An application layer protocol used throughout the internet for translating host names into their associated IP address.
Host Part	An Ip address that is used to uniquely identify a host inside a subnet.
IP Address	A 32-bit address assigned to hosts using TCP/IP. Each address consists of a network number, an optional sub-network number, and host number.
Logical Address	A generic reference to address as defined by layer 3 protocols, which do not have to be concerned with the physical details of the underlying physical media.
Network Broadcast Address	A special address in each classful network that can be used to broadcast a packet to all hosts in the same classful network.
Network Number/Network Address	A number that uses dotted decimal notation like IP address, but the number itself represents all hosts in a single Class A, B, or C network.
Network Part	The portion of an IP address that is either 1,2,or 3 octets long, based on whether the address is in a class A,B, or C network.
Routing Table	A list of routes in a router, with each route listing the destination subnet and mask, the router interface out which to forward packets destined to that subnet, as as needed the next-hop router's IP address.
Subnet Broadcast Address	A special address in each subnet, specifically the largest numeric address in the subnet, designed so that packets sent to this address should be delivered to all hosts in that subnet.
Subnet Number/Subnet Address	A dotted decimal number that represents all addresses in a single subnet.
Subnet Part	Using classful addressing rules, one of three parts of the structure of an IP address, with the subnet part unquely identifying different subnets of a classful IP network.
Access Link	In frame relay, the physical serial link that connects a frame relay DTW device, usually a router, to a frame relay switch.
Back to Back Link	A serial link between two routers, created without CSU/DSU by connecting a DTE cable to one router and a DCE cable to the other. Typically used in labs.
Clocking	The process of supplying a signal over a cable, either on a separate ping on a serial cable, or as part of the signal transitions in the transmitted signal.
CSU/DSU	Channel Service Unit/Digital Service Unit. A device that understands the Layer 1 details of serial links installed by a Telco and how to use a serial cable to communicate with networking equipment such as routers.
DCE	Data Communications Equipment. From a physical layer perspective, the device providing the clocking on a WAN link, typically a CSU/DSU, is the DCE.
DTE	Data Terminal Equiptment. From a Layer 1 perspective, the DTE synchronizes its clock based on the clock sent by the DCE.
DS0	Digital Signal Level 0. A 64-kbps line or channel of a faster line inside a telco whose arigins are to support a single voice call.
DS1	Digital Signal Level 1. A 1.54-mbps line from the telco, Also called a T1 line.
Frame Relay	An international standard data-link protocol that defines the capabilities to create a frame-switched service, allowing DTE devices to send data to many other devices using a single physical connection to the frame relay service.
HDLC	High-Level Data Link Control. A bit-oriented synchronous data link layer protocol developed by the ISO.
Leased Line	A serial communications curcuit between two points, provided by some service provider, typically a telephone company telco.
Packet Switching	A generic reference to network services, typically WAN services, in which the service examines the contents of the transmitted data to make some type of forwarding decision.
PPP	Point to Point Protocol. A protocol that provides router-to-router and host-to-network connections over synchronous point-to-point and asynchronous point-to-point circuits.
Serial Cable	A type of cable with many different styles of connectors used to connect a router to an external CSU/DSU on a leased line intalation.
Synchronous	The imposition of time on a bit stream. A device will try to use the same speed as another device on the other end of the serial link.
T1	A line from the telco that allows tranmission of data at 1.55 mbps, with the ability to treat the line as 24 different 64 kbps DS0 channels.
Virtual Circuit	In packet-switched services like frame relay, VC refers to the ability of two DTE devices typically routers to send and receive data directly to each other, which is the same function as a leased line, but doing so without a physical circuit.
Decapsulation	On a computer that receives data over a network, a process in which the device interprets the lower layer headers, and when finished with each header, removes the header, revealing the next higher layer.
Same-Layer Interaction	Communication between two networking devices for the purpose of the functions defined at a particular layer of a networking model. Both networking devices are using the same layer.
Adjacent-Layer Interaction	Two adjacent layers in a networking architectural model work together, with the lower layer providing services to the higher layer.
Encapsulation	The placement of data from a higher layer protocol behind the header of the next lower layer protocol.
Networking Model	A generic term referring to any set of protocols and standards collected into a comprehensive grouping that, when followed by all devices in a network, allows all devices to communicate. Just like the TCP/IP and OSI Model.
Protocol Data Unit	A generic term referring to the header defined by some layer of a networking model and the data encapsulated by the header of that layer.
Segment	A term used to describe a TCP header and its encapsulated data.
Frame	A term referring to a data-link header and trailer, plus the data encapsulated between the header and the trailor.
Packet	A logical grouping of information that includes the network layer header and encapsulated data.
Ethernet: Speed, Alternative name, IEEE name, Cable type and length	Speed: 10 mbps. Alternative name: 10Base-T. IEEE name: 802.3. Cable type and length: Copper, 100m
Fast Ethernet: Speed, Alternative name, IEEE name, Cable type and length	Speed: 100mbps. Alternative name: 100Base-TX. IEEE name: 802.3u. Cable type and length: copper, 100m
Gigabit Ethernet: Speed, Alternative name, IEEE name, Cable type and length	Speed: 1000mbps. Alternative name: 1000Base-LX, 1000Base-SX, 1000Base-T. IEEE name: 802.3z and 802.ab. Cable type and length: Fiber 550m(SX). 5km(LX). 100m
Twisted Pair	Consisting of two insulated wires, with the wires twisted around each other in a spiral.
Switched Ethernet	An ethernet that uses a switch, so that devices connected to one switch port do not have to contend to use the bandwidth available on another port. Devices do not share the bandwidth.
Switch	A network device that filters, forwards, and floods ethernet frames based on the destination address of each frame.
Straight-Through Cable	In ethernet, a cable that connects the wire on pin 1 on one end of the cable to pin 1 on the other end.
Shared Ethernet	An ethernet that uses a hub, or even the original coaxial cableing, which results in the devices having to take turns sending data, sharing the bandwidth.
Hub	A LAN device that provides a centeralized connection point for LAN cabling, repeating only received data out all the ports creating a logical bus. Hubs reside on Layer 1
Half Duplex	Any communication in which only one device at a time can send data.
Full Duplex	Any communication in which two devices can concurrently send and recieve data.
CSMA/CD	Carrier Sense Multiple Access / Collision Detection. Devices ready to transmit data first check the channel for a carrier. If two devices transmit data at the same time, they are reset for a random amount of time, then try to resend again.
Crossover Cable	An ehternet cable that swaps the pair used for transmission on one device to a pair for receiving on the device on the opposits end of the cable. Swaps pins 1,2 and 3,6
10Base-T	10mbps baseband ethernet specification using two-pairs of twisted-pair cabling. Category 3,4,5. One pair receives data, the other pair transmits data. Has a distance of 328 ft per segment.
100Base-TX	A name for fast ehternet standard that uses two-pair copper cabling, a speed of 100mbps, and max cable length of 100m
1000Base-T	A name for Gigabit ethernet standard that uses four-pair copper cabling, a speed of 1000mbps, and a max cable length of 100m