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Manual Chapter: BIG-IP® version 9.4 Global Traffic Manager and Link Controller Implementations Guide: Glossary
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A record

The A record is the ADDRESS resource record that a Global Traffic Manager returns to a local DNS server in response to a name resolution request. The A record contains a variety of information, including one or more IP addresses that resolve to the requested domain name

active unit

In a redundant system, the active unit is the system that currently load balances connections. If the active unit in the redundant system fails, the standby unit assumes control and begins to load balance connections. See also redundant system.

alternate method

The alternate method specifies the second load balancing mode that the Global Traffic Manager uses to load balance a resolution request. See also preferred method, fallback method.

big3d agent

The big3d agent is a monitoring agent that collects metrics information about server performance and network paths between a data center and a specific local DNS server. The Global Traffic Manager uses the information collected by the big3d agent for dynamic load balancing.

BIND (Berkeley Internet Name Domain)

BIND is the most common implementation of the Domain Name System (DNS). BIND provides a system for matching domain names to IP addresses. For more information, refer to


A certificate is an online credential signed by a trusted certificate authority and used for SSL network traffic as a method of authentication.

CNAME record

A canonical name (CNAME) record acts as an alias to another domain name. A canonical name and its alias can belong to different zones, so the CNAME record must always be entered as a fully qualified domain name. CNAME records are useful for setting up logical names for network services so that they can be easily relocated to different physical hosts.

Configuration utility

The Configuration utility is the browser-based application that you use to configure the BIG-IP system.

data center

A data center is a physical location that houses one or more Global Traffic Managers, BIG-IP systems, or host machines.

default wildcard virtual server

A default wildcard virtual server has an IP address and port number of or *:* or "any":"any". This virtual server accepts all traffic that does not match any other virtual server defined in the configuration. See also wildcard virtual server.

domain name

A domain name is a unique name that is associated with one or more IP addresses. Domain names are used in URLs to identify particular Web pages. For example, in the URL, the domain name is

Dynamic Ratio load balancing method

Dynamic Ratio mode is like Ratio mode (see Ratio method), except that ratio weights are based on continuous monitoring of the servers and are therefore continually changing. Dynamic Ratio load balancing can be implemented on RealNetworks® RealServer platforms, on Microsoft® Windows platforms equipped with Windows Management Instrumentation (WMI), or on a server equipped with either the UC Davis SNMP agent or Windows 2000 Server SNMP agent.

EAV (Extended Application Verification)

EAV is a health check that verifies an application on a node by running that application remotely. EAV health check is only one of the three types of health checks available on an Link Controller. See also health check, health monitor, and external monitor.

ECV (Extended Content Verification)

ECV is a health check that allows you to determine if a node is up or down based on whether the node returns specific content. ECV health check is only one of the three types of health checks available on an Link Controller. See also health check.

external authentication

External authentication refers to the process of using a remote server to store data for the purpose of authenticating users or applications attempting to access the Link Controller.

external monitor

An external monitor is a user-supplied health monitor. See also health check, health monitor.

external VLAN

The external VLAN is a default VLAN on the BIG-IP system. In a basic configuration, this VLAN has the administration ports locked down. In a normal configuration, this is typically a VLAN on which external clients request connections to internal servers. See also VLAN.


Fail-over is the process whereby a standby unit in a redundant system takes over when a software failure or a hardware failure is detected on the active unit.

fail-over pair

See redundant system.

fallback method

The fallback method is the third method in a load balancing hierarchy that the Global Traffic Manager uses to load balance a resolution request. The Global Traffic Manager uses the fallback method only when the load balancing modes specified for the preferred and alternate methods fail. Unlike the preferred method and the alternate method, the fallback method uses neither server nor virtual server availability for load balancing calculations. See also preferred method, alternate method.

floating IP address

A floating self IP address is an additional self IP address for a VLAN that serves as a shared address by both units of a BIG-IP redundant system.

health check

A health check is a Link Controller feature that determines whether a node is up or down. Health checks are implemented through health monitors. See also EAV, ECV, external monitor, and health monitor.

health monitor

A health monitor checks a node to see if it is up and functioning for a given service. If the node fails the check, it is marked down. Different monitors exist for checking different services. See also health check, EAV, ECV, and external monitor.


The physical port on a BIG-IP system is called an interface.

internal VLAN

The internal VLAN is a default VLAN on the BIG-IP system. In a basic configuration, this VLAN has the administration ports open. In a normal configuration, this is a network interface that handles connections from internal servers.


The iQuery protocol is used to exchange information between Global Traffic Managers and BIG-IP systems. The iQuery protocol is officially registered with IANA for port 4353, and works on UDP and TCP connections.


An iRule is a user-written script that controls the behavior of a connection passing through the Link Controller. iRules™ are an F5 Networks feature and are frequently used to direct certain connections to a non-default load balancing pool. However, iRules can perform other tasks, such as implementing secure network address translation and enabling session persistence.

link load balancing

Link load balancing is defined as managing traffic across multiple Internet or wide-area network (WAN) gateways.

load balancing method

A particular method of determining how to distribute connections across a load balancing pool.

load balancing pool

See pool.

local DNS

A local DNS is a server that makes name resolution requests on behalf of a client. With respect to the Global Traffic Manager, local DNS servers are the source of name resolution requests. Local DNS is also referred to as LDNS.

local traffic management (LTM)

Local traffic management (LTM) is the process of managing network traffic that comes into or goes out of a local area network (LAN), including an intranet.


Member is a reference to a node when it is included in a particular load balancing pool. Pools typically include multiple member nodes.


The Link Controller uses monitors to determine whether nodes are up or down. There are several different types of monitors and they use various methods to determine the status of a server or service.

name resolution

Name resolution is the process by which a name server matches a domain name request to an IP address, and sends the information to the client requesting the resolution.

name server

A name server is a server that maintains a DNS database, and resolves domain name requests to IP addresses using that database.


The named daemon manages domain name server software.

Network Time Protocol (NTP)

Network Time Protocol functions over the Internet to synchronize system clocks to Universal Coordinated Time. NTP provides a mechanism to set and maintain clock synchronization within milliseconds.

NS record

A name server (NS) record is used to define a set of authoritative name servers for a DNS zone. A name server is considered authoritative for some given zone when it has a complete set of data for the zone, allowing it to answer queries about the zone on its own, without needing to consult another name server.


A pool is composed of a group of network devices (called members). The Link Controller load balances requests to the nodes within a pool based on the load balancing method and persistence method you choose when you create the pool or edit its properties.

pool member

A pool member is a server that is a member of a load balancing pool.


A port can be represented by a number that is associated with a specific service supported by a host. Refer to the Services and Port Index for a list of port numbers and corresponding services.

preferred method

The preferred method specifies the first load balancing mode that the Global Traffic Manager uses to load balance a resolution request. See also alternate method, fallback method.


A ratio is a parameter that assigns a weight to a virtual server for load balancing purposes.

redundant system

Redundant system refers to a pair of units that are configured for fail-over. In a redundant system, there are two units, one running as the active unit and one running as the standby unit. If the active unit fails, the standby unit takes over and manages connection requests.

resource record

A resource record is a record in a DNS database that stores data associated with domain names. A resource record typically includes a domain name, a TTL, a record type, and data specific to that record type. See also A record, CNAME record, NS record.

secondary DNS

The secondary DNS is a name server that retrieves DNS data from the name server that is authoritative for the DNS zone.

self IP address

Self IP addresses are the IP addresses owned by the BIG-IP system that you use to access the internal and external VLANs.


Service refers to services such as TCP, UDP, HTTP, and FTP.

Setup utility

The Setup utility walks you through the initial system configuration process. You can run the Setup utility from the Configuration utility start page.

SSL (Secure Sockets Layer)

SSL is a network communications protocol that uses public-key technology as a way to transmit data in a secure manner.

standby unit

A standby unit in a redundant system is a unit that is always prepared to become the active unit if the active unit fails.


A subdomain is a sub-section of a higher level domain. For example, .com is a high level domain, and is a subdomain within the .com domain.

synchronization group

A synchronization group is a group of Global Traffic Managers that synchronize system configurations and zone files (if applicable). All synchronization group members receive broadcasts of metrics data from the big3d agents throughout the network. All synchronization group members also receive broadcasts of updated configuration settings from the Global Traffic Manager that has the latest configuration changes.

virtual server

Virtual servers are a specific combination of virtual address and virtual port, associated with a content site that is managed by an Link Controller or other type of host server.


VLAN stands for virtual local area network. A VLAN is a logical grouping of network devices. You can use a VLAN to logically group devices that are on different network segments.

wildcard virtual server

A wildcard virtual server is a virtual server that uses an IP address of, * or "any". A wildcard virtual server accepts connection requests for destinations outside of the local network. Wildcard virtual servers are included only in Transparent Node Mode configurations. See also default wildcard virtual server.


In DNS terms, a zone is a subset of DNS records for one or more domains.

zone file

In DNS terms, a zone file is a database set of domains with one or many domain names, designated mail servers, a list of other name servers that can answer resolution requests, and a set of zone attributes, which are contained in an SOA record.

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