Network + Guide To Network Chapter 8 , 8 edition

tag

A VLAN identifier added to a frame's header according to specifications in the 802.1Q standard.

classless addressing

An IP addressing convention that alters the rules of classful IPv4 addressing to create subnets in a network.

VLAN hopping

An attack in which the attacker generates transmissions that appear, to the switch, to belong to a protected VLAN.

native VLAN

An untagged VLAN on a switch that will automatically receive all untagged frames.

magic number

In the context of calculating subnets, the difference between 256 and the interesting octet (any octet in the subnet whose value is something other than 0 or 255). It can be used to calculate the network IDs in all the subnets of a larger network.

site prefix

The first four blocks or 64 bits of an IPv6 address that normally identify the network. Also called global routing prefix.

global routing prefix

The first four blocks or 64 bits of an IPv6 address that normally identify the network. Also called site prefix.

trunk port

The interface on a switch capable of managing traffic from multiple VLANs.

access port

The interface on a switch used for an end node. Devices connected to access ports are unaware of VLAN information.

native VLAN mismatch

A configuration error where switch ports on each end of a trunk are configured with different native VLAN assignments. Also called a VLAN mismatch.

VLAN mismatch

A configuration error where switch ports on each end of a trunk are configured with different native VLAN assignments. Also called a native VLAN mismatch.

ANDing

A logical process of combining bits.

VLAN (virtual local area network or virtual LAN)

A network within a network that is logically defined by grouping ports on a switch so that some of the local traffic on the switch is forced to go through a router, thereby limiting the traffic to a smaller broadcast domain.

default VLAN

A preconfigured VLAN on a switch that includes all the switch's ports and cannot be renamed or deleted.

ip helper-address

A robust Cisco command that can be configured to create and send helper messages that support several types of UDP traffic, including DHCP, TFTP, DNS, and TACACS+.

CIDR notation

A shorthand method for denoting the distinction between network and host bits in an IP address.

CIDR (Classless Interdomain Routing)

A shorthand method for identifying network and host bits in an IP address.

DHCP relay agent

A small application that works with a centrally managed DHCP server to provide DHCP assignments to multiple subnets and VLANs.

VLSM (Variable Length Subnet Mask)

A subnetting method that allows subnets to be further subdivided into smaller and smaller groupings until each subnet is about the same size as the needed IP address space.

managed switch

A switch that can be configured via a command-line interface or a web-based management GUI, and sometimes can be configured in groups.

unmanaged switch

A switch that provides plug-and-play simplicity with minimal configuration options and has no IP address assigned to it.

VTP (VLAN Trunk Protocol)

Cisco's protocol for exchanging VLAN information over trunks.

CIDR block

In CIDR notation, the forward slash plus the number of bits used for the network ID. For example, the CIDR block for 199.34.89.0/22 is /22.

802.1Q

The IEEE standard that specifies how VLAN and trunking information appears in frames and how switches and bridges interpret that information.

trunking

The aggregation of multiple logical connections in one physical connection between connectivity devices. In the case of VLANs, a trunk allows two switches to manage and exchange data between multiple VLANs.