Network+ Guide to Network (7th Edition) - Chapter 10 Key Terms

tag

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

TRILL (Transparent Interconnection of Lots of Links)

A multipath, link-state protocol (using IS-IS) developed by the IETF and designed to replace STP.

bridged mode

A type of network connection in which a vNIC accesses a physical network using the host machine's NIC. In other words, the virtual interface and the physical interface are bridged. The bridged vNIC, however, obtains its own IP address, default gateway, and subnet mask information from the physical LAN's DHCP server.

BPDU (Bridge Protocol Data Unit)

A type of network message that transmits STP information between switches.

SPB (Shortest Path Bridging)

As described in IEEE's 802.1aq standard, a descendent of the Spanning Tree Protocol that can detect and correct for network changes much more quickly.

MSTP (Multiple Spanning Tree Protocol)

As described in IEEE's 802.1s standard, a version of the Spanning Tree Protocol that can detect and correct for network changes much more quickly.

software defined networking (SDN)

The virtualization of network services in which a network controller manages these services instead of the services being directly managed by the hardware devices involved.

vNIC (virtual network interface card)

A logically defined network interface associated with a virtual machine.

unmanaged switch

A switch that provides plug-and-play simplicity with minimal configuration options and has no IP address assigned to it. Unmanaged switches are inexpensive, but their capabilities are limited.

VMware

A vendor that supplies the most popular types of workstation and server virtualization software. Used casually, the term VMware may also refer to the virtualization software distributed by the company.

virtual workstation

A workstation that exists as a virtual machine, created and managed by virtualization software on a host, or physical, computer.

virtual bridge

An interface connecting a vNIC with a virtual or physical network, or a port on a virtual switch.

host

(1) Any computer or device on a network that provides a resource such as an application or data. (2) In the context of virtualization, the physical computer on which virtualization software operates and manages guests.

network controller

(1) In the context of virtualization, a central console that manages virtual devices, services, and appliances. For example, the newest, not-yet-released Windows Server will provide a Network Controller role for managing both physical and virtual network infrastructure. (2) Sometimes used to refer to a device's NIC or network adapter.

supernet mask

A 32-bit number that, when combined with a device's IPv4 address, indicates the kind of supernet to which the device belongs. Whereas the subnet mask moves the network prefix to the right, the supernet mask moves the network prefix to the left, thereby taking up fewer digits than the related classful network prefix.

ip helper-address

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

DHCP relay agent

A DHCP configuration that provides DHCP service to multiple VLANs. The relay agent receives a DHCP-related message, then creates its own message to send the specified DHCP traffic beyond the broadcast domain.

wireless controller

A central management console for all of the APs on a network.

BID (Bridge ID)

A combination of a 2-byte priority field and a bridge's MAC address, used in STP (Spanning Tree Protocol) to select a root bridge.

VLAN pooling

A feature on wireless controllers that groups multiple VLANs into a single VLAN group, or pool, and then dynamically assigns wireless clients to each successive VLAN in the pool.

ANDing

A logical process of combining bits. In ANDing, a bit with a value of 1 combined, or ANDed, with another bit having a value of 1 results in a 1. A bit with a value of 0 ANDed with any other bit (either 0 or 1) results in a 0.

virtual switch

A logically defined device that is created and managed by virtualization software and that operates at the Data Link layer to pass frames between nodes. Ports on a virtual switch connect virtual machines with a network, whether virtual or physical, through the host's physical NIC.

virtual terminal

A machine at the technician's location that provides for remote configuration of a switch.

VLAN (virtual local area network)

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. A VLAN can consist of any type of network node in any geographic location and can incorporate nodes connected to different switches.

default VLAN

A preconfigured VLAN on a switch that includes all of the switch's ports and cannot be renamed or deleted. The switch might be preconfigured with other VLANs as well, depending on the device and manufacturer.

CAPWAP (Control and Provisioning of Wireless Access Points)

A proprietary protocol created by Cisco to replace LWAPP. Both LWAPP and CAPWAP make centralized wireless management possible, and both direct all wireless frames to the wireless controller by adding extra headers to the frames.

OpenFlow

A protocol that serves as a common language in SDN (software defined networking) to bridge the gap between virtualized service applications and a network's physical devices, ensuring that the applications make decisions rather than the devices themselves operating independently from the virtualized services.

thick AP

A self-contained AP that can do its job without relying on a higher-level management device.

virtual server

A server that exists as a virtual machine, created and managed by virtualization software on a host, or physical, computer.

CIDR notation

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

thin AP

A simple AP that must be configured from the wireless controller's console in order to function.

stack master

A single switch that hosts the VLAN database for all switches on a network.

BPDU guard

A software configuration on a switch's access ports that blocks certain types of BPDUs from being sent to or received by the devices, such as workstations and servers, connected to these ports. A BPDU guard is necessary because network hosts should not be considered as possible paths to other destinations.

BPDU filter

A software configuration that can be used to disable STP on specific ports, such as the port leading to the network's demarc. A BPDU filter prevents access to network links that should not be considered when plotting STP paths in a network.

VRRP (Virtual Router Redundancy Protocol)

A standard that assigns a virtual IP address to a group of routers. At first, messages routed to the virtual IP address are handled by the master router. If the master router fails, backup routers stand in line to take over responsibility for the virtual IP address.

route aggregation

A supernet configuration implemented for the purpose of reducing the number of routing table entries by combining several entries, one for each network, into one entry that represents multiple networks.

out-of-band management

A switch management option that provides on-site infrastructure access when the network is down or complete remote access in cases of connectivity failures on the network, such as via a cellular signal, in order to interface with a switch.

in-band management

A switch management option, such as Telnet, that uses the existing network and its protocols to interface with a switch.

managed switch

A switch that can be configured via a command-line interface and sometimes can be configured in groups. Usually, they are assigned their own IP addresses. VLANs can only be implemented through managed switches.

STP (Spanning Tree Protocol)

A switching protocol defined in IEEE 802.1D. STP operates in the Data Link layer to prevent traffic loops by calculating paths that avoid potential loops and by artificially blocking links that would complete a loop. Given changes to a network's links or devices, STP recalculates its paths.

host-only mode

A type of network connection in which VMs on a host can exchange data with each other and with their host, but they cannot communicate with any nodes beyond the host. In other words, the vNICs never receive or transmit data via the host machine's physical NIC.

NAT mode

A type of network connection in which a vNIC relies on the host machine to act as a NAT device. In other words, the VM obtains IP addressing information from its host, rather than a server or router on the physical network. To accomplish this, the virtualization software acts as a DHCP server.

VirtualBox

A virtualization software platform from Oracle.

LWAPP (Lightweight Access Point Protocol)

A wireless protocol created by Cisco that makes centralized wireless management possible. LWAPP directs all wireless frames to the wireless controller by adding extra headers to the frames, but it is also considered a lightweight protocol because the headers are relatively small.

management console

A workstation, such as a laptop, that is connected to a switch's console port and allows for changes to be made to a switch's configurations.

virtual IP address

An IP address that can be shared by a group of routers.

CIDR (Classless Interdomain Routing)

An IP addressing and subnetting method in which network and host information is manipulated without adhering to the limitations imposed by traditional network class distinctions. CIDR is also known as classless routing or supernetting. Older routing protocols, such as RIP, are not capable of interpreting CIDR addressing schemes.

classful addressing

An IP addressing convention that adheres to network class distinctions, in which the first 8 bits of a Class A address, the first 16 bits of a Class B address, and the first 24 bits of a Class C address are used for network information.

VLAN hopping attack

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

virtual appliance

An image that includes the appropriate operating system, software, hardware specifications, and application configuration necessary for a prepackaged solution to run properly on a virtual machine.

KVM (Kernel-based Virtual Machine)

An open source virtualization package designed for use with Linux systems.

native VLAN

An untagged VLAN on a switch that will automatically receive all untagged frames. Options for native VLANs vary according to the switch manufacturer and model.

RSTP (Rapid Spanning Tree Protocol)

As described in IEEE's 802.1w standard, a version of the Spanning Tree Protocol that can detect and correct for network changes much more quickly.

HSRP (Hot Standby Routing Protocol)

Cisco's proprietary standard, similar to VRRP, that assigns a virtual IP address to a group of routers. At first, messages routed to the virtual IP address are handled by the active router. If the active router fails, standby routers stand in line to take over responsibility for the virtual IP address.

VTP (VLAN trunking protocol)

Cisco's protocol for exchanging VLAN information over trunks. VTP allows one switch on a network to centrally manage all VLANs.

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.

supernet

In IPv4, a type of subnet that is created by moving the subnet boundary to the left instead of the right and using bits that normally would be reserved for network information instead of using bits reserved for host information.

routing prefix

In an IPv6 address, the first four blocks (or 64 bits) that identify the network and serve as the network ID. Also called network prefix.

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). The magic number can also be calculated by raising 2 to the power of the number of bits in the host portion of the subnet mask using the formula 2^h=magic number. The magic number can be used to calculate the network IDs in all the subnets of the larger network.

guest

In the context of virtualization, a virtual machine operated and managed by a virtualization program.

Hyper-V

Microsoft's virtualization software package. Hyper-V was first available with Windows Server 2008, and is now available in some 64-bit versions of Windows 8.1 as well.

SAID (security association identifier)

Part of a VLAN configuration that indicates to other connectivity devices which VLAN a transmission belongs to. By default, Cisco switches assign a VLAN the SAID of 100,000 plus the VLAN number (such as 100,000+12).

slash notation

See CIDR notation.

classless routing

See CIDR.

supernetting

See CIDR.

virtual machine manager

See hypervisor.

network number

See network ID.

network prefix

See network ID.

router summarization

See route aggregation.

virtual adapter

See vNIC.

virtual console

See virtual terminal.

WLAN controller

See wireless controller.

Wi-Fi controller

See wireless controller.

802.1s

The IEEE standard that describes MSTP (Multiple Spanning Tree Protocol), which evolved from STP (Spanning Tree Protocol).

802.1w

The IEEE standard that describes RSTP (Rapid Spanning Tree Protocol), which evolved from STP (Spanning Tree Protocol).

802.1aq

The IEEE standard that describes SPB (Shortest Path Bridging) and that evolved from STP (Spanning Tree Protocol).

802.1D

The IEEE standard that describes, among other things, bridging and STP (Spanning Tree Protocol).

802.1Q

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

data plane

The actual contact made between physical devices and data transmissions as these messages traverse a network.

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.

extended network prefix

The combination of an IP address's network ID and subnet information. By interpreting the address's extended network prefix, a device can determine the subnet to which an address belongs.

hypervisor

The element of virtualization software that manages multiple guest machines and their connections to the host (and by association, to a physical network). A hypervisor is also known as a virtual machine manager.

virtualization

The emulation of all or part of a computer or network.

trunk port

The interface on a switch capable of managing traffic from multiple VLANs. A trunk is a link configured between two switches' trunk ports.

access port

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

root port

The port on a bridge that is closest to the root bridge. On any bridge, the root port is the only port that can forward frames toward the root bridge.

designated port

The port on a segment (which is the link between two bridges) that provides the shortest path to a specific destination. Only the designated port on a segment can transmit network traffic because STP disables links that are not part of the shortest path.

network ID

The portion of an IP address common to all nodes on the same network or subnet.

route prefix

The prefix in an IPv6 address that identifies a route. Because route prefixes vary in length, slash notation is used to define them. For example, the route prefix indicated by 2608:FE10::/32 includes all subnets whose prefixes begin with 2608:FE1O and, consequently, all interfaces whose IP addresses begin with 2608:FE10.

control plane

The process of decision making, such as routing, blocking, and forwarding, that is performed by protocols.

root bridge

The single bridge on a network selected by STP to provide the basis for all subsequent path calculations. Also called master bridge.

prefix mask

The usually optional slash notation at the end of an IPv6 address that indicates the number of bits used by the network prefix.