CCNA 200-301 Key Vocabulary Terms.

what is adjacent-layer interaction?

The topic of how on one computer, two adjacent layers in in a network model work together, with the lower layer providing services to the higher layer.

De-encapsulation

On a computer that receives data over a network, the process in which the device interprets the lower-layer headers and, when finished with each header, removes the header, revealing the next-higher-layer PDU.

Encapsulation

The placement pf data from a higher layer protocol behind the header or in-between an ethernet header and trailer.

Frame

A term referring to a data link header and trailer, plus the data encapsulated between the header and trailer.

These are sent on layer 1 for TCP/IP and layer 2 for OSI

what is a packet?

A logical grouping of bytes that includes the network layer header and encapsulated data.

PDU

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 (sometimes the trailer as well ) of that layer, does not include any lower layers headers and trailers just like a packet.

What is same-layer interaction?

The communication between two networking devices for the purposes of the functions defined at ta particular layer of a networking model, with that communication happening by using a header defined by the layer of the model. The two devices set values in the header, send the header and encapsulated data, with the receiving devices interpreting the header to decide what action to take.

Exchanging Frames, Packets etc and then determining the next action is simpler cisco.

segment

In TCP, a term used to describe a TCP header and its encapsulated data (also called an L4PDU). Also in TCP, the process of accepting a large chunk of data from the application layer and breaking it into smaller pieces that fit into TCP segments. In Ethernet, a segment is either a single Ethernet cable or a single collision domain (no matter how many cables are used).

In TCP/Ip a segment also called a L4PDU refers to the TCP header and it's encapsulated data.

In ethernet this refers to a single ethernet cable of collision domain.

Ethernet

A series of LAN standards defined by the IEEE, originally invented by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation.

IEEE

Institute of Electrical and Electronics Engineers. A professional organization that develops communications and network standards, among other activities.

ethernet link

A generic term for any physical link between two Ethernet nodes, no matter what type of cabling is used.

NIC

A Network Interface Card is a piece of hardware that allows a computer to connect to a network.

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 of the cable, pin 2 on one end to pin 2 on the other end, and so on.

crossover cable

An Ethernet cable that swaps the pair used for transmission on one device to a pair used for receiving on the device on the opposite end of the cable. In 10BASE-T and 100BASE-TX networks, this cable swaps the pair at pins 1,2 to pins 3,6 on the other end of the cable, and the pair at pins 3,6 to pins 1,2 as well.

Ethernet address

A 48-bit (6-byte) binary number, usually written as a 12-digit hexadecimal number, used to identify Ethernet nodes in an Ethernet network. Ethernet frame headers list a destination and source address field, used by the Ethernet devices to deliver Ethernet frames to the correct destination.

MAC address

A standardized data link layer address that is required for every device that connects to a LAN. Ethernet MAC addresses are 6 bytes long and are controlled by the IEEE. Also known as a hardware address, a MAC layer address, and a physical address.

unicast address

Generally, any address in networking that represents a single device or interface, instead of a group of addresses (as would be represented by a multicast or broadcast address).

Broadcast Address

Generally, any address that represents all devices, and can be used to send one message to all devices. In Ethernet, the MAC address of all binary 1s, or FFFF.FFFF.FFFF in hex. For IPv4, see subnet broadcast address.

Frame Check Sequence (FCS)

A field in many data link trailers used as part of the error-detection process.

Multimode Fiber (MMF)

Type of fiber-optic cable that uses LEDs and emits light at multiple angles.

Single-mode fiber (SMF)

Fiber-optic cable that allows only a single light wave to pass down the cable.

EMI

Electromagnetic Interference

Core

in fiber-optic cabling, the center cylinder of the cable, made of fiberglass, through which light passes is the CORE.

Leased line

A serial communications circuit between two points, provided by some service provider, typically a telephone company (telco). Because the telco does not sell a physical cable between the two endpoints, instead charging a monthly fee for the ability to send bits between the two sites, the service is considered to be a leased service.

WAN

Wide Area Network

LAN

Local Area Network

Telco

A common abbreviation for telephone company.

Most often used in reference to the telco box.

serial link

most commonly used to connect to leased lines and frame relay access links if used at all nowadays.

HDLC (High-level Data Link Control)

A bit-oriented synchronous data link layer protocol developed by the International Organization for Standardization (ISO).

Ethernet over MPLS (Multi Protocol Label Switching)

A term referring to an ethernet WAN service.

default router (default gateway)

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.

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, and as needed, the next-hop router's IP address.

IP subnet

Subdivisions of a Class A, B, or C network, as configured by a network administrator. Subnets allow a single Class A, B, or C network to be used instead of multiple networks, and still allow for a large number of groups of IP addresses, as is required for efficient IP routing.

Routing protocols

Examples of routing protocols include Enhanced Interior Gateway Routing Protocol (EIGRP), Open Shortest Path First (OSPF), and Routing Information Protocol (RIP).

dotted decimal notation

The format used for IP version 4 addresses, in which four decimal values are used, separated by periods (dots).

IPv4 address

In IP version 4 (IPv4), a 32-bit address assigned to hosts using TCP/IP. Each address consists of a network number,

unicast IP address

An IP address that represents a single interface. In IPv4, these addresses come from the Class A, B, and C ranges.

Subnetting

The process of subdividing a Class A, B, or C network into smaller groups called subnets.

ARP

Address Resolution Protocol. An Internet protocol used to map an IP address to a MAC address. Defined in RFC 826.

Ping

An Internet Control Message Protocol (ICMP) echo message and its reply; ping often is used in IP networks to test the reachability of a network device.

Most commonly used and needed troubleshooting tool.

startup-config file

In Cisco IOS switches and routers, the name of the file that resides in NVRAM memory, holding the device's configuration that will be loaded into RAM as the running-config file when the device is next reloaded or powered on.

Flood

The result of the LAN switch forwarding process for broadcasts and unknown unicast frames. Switches forward these frames out all interfaces, except the interface in which the frame arrived. Switches also flood multicasts by default, although this behavior can be changed.

local username

local username

A username (with matching password), configured on a router or switch. It is considered local because it exists on the router or switch, and not on a remote server.

AAA

Authentication, authorization, and accounting. Authentication confirms the identity of the user or device. Authorization determines what the user or device is allowed to do. Accounting records information about access attempts, including inappropriate requests.

AAA server

AAA server

A server that holds security information and provides services related to user login, particularly authentication (is the user who he says he is?), authorization (once authenticated, what do we allow the user to do?), and accounting (tracking the user).

VLAN interface

A configuration concept inside Cisco switches, used as an interface between IOS running on the switch and a VLAN supported inside the switch, so that the switch can assign an IP address and send IP packets into that VLAN.

history buffer

In a Cisco router or switch, the function by which IOS keeps a list of commands that the user has used in this login session, both in EXEC mode and configuration mode. The user can then recall these commands for easier repeating or making small edits and issuing similar commands.

name resolution

The process by which an IP host discovers the IP address associated with a hostname, often involving sending a DNS request to a DNS server, with the server supplying the IP address used by a host with the listed hostname.

autonegotiation

autonegotiation

An IEEE standard mechanism (802.3u) with which two nodes can exchange messages for the purpose of choosing to use the same Ethernet standards on both ends of the link, ensuring that the link functions and functions well.

It chooses what it thinks is the best duplex (full or half) based on the information it has of the two links.

full duplex

Generically, any communication in which two communicating devices can concurrently send and receive data. In Ethernet LANs, the allowance for both devices to send and receive at the same time, allowed when both devices disable their CSMA/CD logic.

half duplex

Generically, any communication in which only one device at a time can send data. In Ethernet LANs, the normal result of the CSMA/CD algorithm that enforces the rule that only one device should send at any point in time.

802.1Q

The IEEE standardized protocol for VLAN trunking, which also includes RSTP details.

We use this standard exclusively at work.

trunk

In campus LANs, an Ethernet segment over which the devices add a VLAN header that identifies the VLAN in which the frame exists.

typically trunks are what you want to configure to pass data to the next device also known as untagged.

trunking administrative mode

trunking administrative mode

The configured trunking setting on a Cisco switch interface, as configured with the switchport mode command.

virtual LAN (VLAN)

A group of devices, connected to one or more switches, with the devices grouped into a single broadcast domain through switch configuration. VLANs allow switch administrators to separate the devices connected to the switches into separate VLANs without requiring separate physical switches, gaining design advantages of separating the traffic without the expense of buying additional hardware.

VLAN Trunking Protocol (VTP)

A Cisco-proprietary messaging protocol used between Cisco switches to communicate configuration information about the existence of VLANs, including the VLAN ID and VLAN name.

VTP transparent mode

VTP transparent mode

One of three VTP operational modes. Switches in transparent mode can configure VLANs, but they do not tell other switches about the changes, and they do not learn about VLAN changes from other switches.

Layer 3 switch

A switch that can also do routing.

we prefer routers however when you need to consider cost and you don't need as much processing power this is a good option

access interface

access interface

A LAN network design term that refers to a switch interface connected to end-user devices, configured so that it does not use VLAN trunking.

This is used when you want an ethernet link to go to a host. Also called untagging.

data VLAN

data VLAN

A VLAN used by typical data devices connected to an Ethernet, like PCs and servers. Used in comparison to a voice VLAN.

voice VLAN

VLAN defined for use by IP Phones, with the Cisco switch notifying the phone about the voice VLAN ID so that the phone can use 802.1Q frames to support traffic for the phone and the attached PC (which uses a data VLAN)

AKA whatever Vlan is assigned and configured with the IP's alloted for VOIP phones.

static access interface

A LAN network design term, synonymous with the term access interface, but emphasizing that the port is assigned to one VLAN as a result of static configuration rather than through some dynamic process.

Spanning Tree Protocol (STP)

A protocol defined by IEEE standard 802.ID. Allows switches and bridges to create a redundant LAN, with the protocol dynamically causing some ports to block traffic, so that the bridge/switch forwarding logic will not cause frames to loop indefinitely around the LAN

blocking state

In STP, a port state in which no received frames are processed and the switch forwards no frames out the interface, with the exception of STP messages.

BPDU Guard

A Cisco switch feature that listens for incoming STP BPDU messages, disabling the interface if any are received. The goal is to prevent loops when a switch connects to a port expected to only have a host connected to it.

bridge ID

An 8-byte identifier for bridges and switches used by STP and RSTP. It is composed of a 2-byte priority field followed by a 6-byte System ID field that is usually filled with a MAC address.

BPDU

Bridge protocol data unit. The generic name for Spanning Tree Protocol messages.

designated port

designated port

In both STP and RSTP, a port role used to determine which of multiple interfaces on multiple switches, each connected to the same segment or collision domain, should forward frames to the segment. The switch advertising the lowest-cost Hello BPDU onto the segment becomes the DP.

EtherChannel

EtherChannel

A feature in which up to eight parallel Ethernet segments exist between the same two devices, each using the same speed. May be a Layer 2 EtherChannel, which acts like a single link for forwarding and Spanning Tree Protocol logic, or a Layer 3 EtherChannel,which acts like a single link for the switch’s Layer 3 routing logic.

forward delay

forward delay

An STP timer, defaulting to 15 seconds, used to dictate how long an interface stays in the listening state and the time spent in learning state. Also called the forward delay timer.

Hello BPDU

Hello BPDU

The STP and RSTP message used for the majority of STP communications, listing the root’s bridge ID, the sending device’s bridge ID, and the sending device’s cost with which to reach the root.

PortFast

PortFast

A switch STP feature in which a port is placed in an STP forwarding state as soon as the interface comes up, bypassing the listening and learning states. This feature is meant for ports connected to end-user devices.

root port

root port

In STP and RSTP, the one port on a nonroot switch in which the least-cost Hello is received. Switches put root ports in a forwarding state.

root switch

In STP and RSTP, the switch that wins the election by virtue of having the lowest bridge ID and, as a result, sends periodic Hello BPDUs (default, 2 seconds).

root cost

root cost

The STP cost from a nonroot switch to reach the root switch, as the sum of all STP costs for all ports out which a frame would exit to reach the root.

Rapid Spanning Tree Protocol (RSTP)

Defined in IEEE 802.lw. Defines an improved version of STP that converges much more quickly and consistently than STP (802.Id).

ETH