In a redundant system, the controller which currently load balances connections. If the active unit in the redundant system fails, the standby unit assumes control and begins to load balance connections.
A utility that provides command line access to the BIG/ip Controller.
A statistical monitoring utility that ships on the BIG/ip Controller. This utility provides a snap-shot of statistical information.
A statistical monitoring utility that ships on the BIG/ip Controller. This utility provides real-time information.
A monitoring utility that collects metrics information about paths between a BIG/ip Controller and a specific local DNS server. The big3d utility runs on BIG/ip Controllers and it forwards metrics information to a 3DNS Controller.
BIND (Berkley Internet Name Domain)
The most common implementation of DNS, which provides a system for matching domain names to IP addresses.
A series of filtering criteria used to restrict access to an IP address. The order of the criteria in the chain determines how the filter is applied, from the general criteria first, to the more detailed criteria at the end of the chain.
Cookie persistence is a mode of persistence you can configure on the BIG/ip Controller where the controller stores persistent connection information in a cookie.
default wildcard virtual server
A virtual server that has an IP address and port number of 0.0.0.0:0. This virtual server accepts all traffic which does not match any other virtual server defined in the configuration.
dynamic load balancing modes
Dynamic load balancing modes base connection distribution on live data, such as current server performance and current connection load.
dynamic site content
A type of site content that is automatically generated each time a user accesses the site. Examples are current stock quotes or weather satellite images.
EAV service check
A service check feature that uses an external program to determine if a node is up or down based on whether the node returns specific content. EAV service check is only one of the three types of service checks available on a BIG/ip Controller. See also service check, and external service checker program.
ECV service check
A service check feature that allows you to determine if a node is up or down based on whether the node returns specific content. ECV service check is only one of the three types of service checks available on a BIG/ip Controller. See also service check.
Extended Application Verification (EAV)
A service check feature that uses an external program to determine if a node is up or down based on whether the node returns specific content.
Extended Content Verification (ECV)
A service check feature that allows you to determine if a node is up or down based on whether the node returns specific content.
A network interface on the BIG/ip Controller configured to process destination requests. In a basic configuration, this interface has the administration ports locked down. In a normal configuration, this is typically a network interface on which external clients request connections to internal servers.
external service checker program
A custom program that performs a service check on behalf of the BIG/ip Controller. See also, EAV service check.
An encryption utility that allows secure shell connections to a remote system.
BIG/ip web server
The web server that runs on a BIG/ip Controller and hosts the F5 Configuration utility.
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.
The cable that directly connects the two controller units together in a redundant system.
A dynamic load balancing mode that bases connection distribution on which server currently exhibits the fastest response time to node pings.
FDDI (Fiber Distributed Data Interface)
A multi-mode protocol for transmitting data on optical-fiber cables up to 100 Mbps.
First-Time Boot utility
A utility that walks you through the initial system configuration process. The First-Time Boot utility runs automatically when you turn on a controller for the first time.
A network server which manages one or more virtual servers that the 3DNS Controller uses for load balancing.
ICMP (Internet Control Message Protocol)
An Internet communications protocol used to determine information about routes to destination addresses, such as virtual servers managed by BIG/ip Controllers and 3DNS Controllers.
A network interface on the BIG/ip Controller configured to process source requests. In a basic configuration, this interface has the administration ports open. In a normal configuration, this is typically a network interface which handles connections from internal servers.
A UDP based protocol used to exchange information between BIG/ip Controllers and 3DNS Controllers. The iQuery protocol is officially registered for port 4353.
A last hop is the last hop a connection took to get to the BIG/ip Controller. You can configure the BIG/ip Controller to send packets back to the device from which they originated when that device is part of a last hop pool.
Least Connections mode
A dynamic load balancing mode that bases connection distribution on which server currently manages the fewest open connections.
load balancing mode
A particular method of determining how to distribute connections across an array.
A loopback adapter is a software interface that is not associated with an actual network card. The nPath routing configuration requires you to configure loopback adapters on servers.
MAC (Media Access Control)
A protocol that defines the way workstations gain access to transmission media, most widely used in reference to LANs. For IEEE LANs, the MAC layer is the lower sublayer of the data link layer protocol.
An address used to represent hardware devices on an Ethernet network.
A reference to a node when it is included in a particular virtual server mapping. Virtual server mappings typically include multiple member nodes.
A feature on the BIG/ip Controller that preserves connection and persistence information in a BIG/ip Controller redundant system.
The name server daemon, which manages domain name server software.
NAT (Network Address Translation)
An alias IP address that identifies a specific node managed by the BIG/ip Controller to the external network.
A specific combination of an IP address and port number associated with a server in the array managed by the BIG/ip Controller.
The IP address associated with one or more nodes. This IP address can be the real IP address of a network server, or it can be an alias IP address on a network server.
A node address that the BIG/ip Controller uses to verify the status of multiple nodes. When the BIG/ip Controller uses a node alias to check node status, it pings the node alias. If the BIG/ip Controller receives a response to the ping, it marks all nodes associated with the node alias as up, and if it does not receive a response to the ping, the BIG/ip Controller marks all nodes associated with the node alias as down.
A feature that the BIG/ip Controller uses to determine whether nodes are up or down. Node ping sends standard echo pings to servers and transparent devices. If the server or device responds to the ping, it marks the related nodes up. If the server or device does not respond to the ping, it marks the related nodes down.
The port number or service name hosted by a specific node.
Whether a node is up and available to receive connections, or down and unavailable. The BIG/ip Controller uses the node ping and service check features to determine node status.
A dynamic load balancing mode that bases connection distribution on a combination of two factors: the server that currently hosts the fewest connections, and also has the fastest response time.
A series of related connections received from the same client, having the same session ID. When persistence is turned on, a controller sends all connections having the same session ID to the same node instead of load balancing the connections.
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.
port-specific wildcard virtual server
A wildcard virtual server address that uses a port number other than 0.
A dynamic load balancing mode that bases connection distribution on a combination of two factors: the server that currently hosts the fewest connections, but also has the fastest response time. Predictive mode also ranks server performance over time, and passes connections to servers which exhibit an improvement in performance rather than a decline.
A static load balancing mode that bases connection distribution on server priority levels. The BIG/ip Controller distributes connections in a round robin fashion to all nodes in the highest priority group. If all the nodes in the highest priority group become unavailable, the BIG/ip Controller begins to pass connections to nodes in the next lower priority group.
A rate class determines the volume of traffic allowed through a rate filter.
A parameter that assigns a weight to a virtual server for load balancing purposes.
The Ratio load balancing mode distributes connections across an array of virtual servers in proportion to the ratio weights assigned to each individual virtual server.
A receive expression is the text string that the BIG/ip Controller looks for in the web page returned by a web server during an extended content verification (ECV) service check.
A pair of controllers that are configured for fail-over. In a redundant system, there are two controller 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.
remote administrative IP address
An IP address from which a controller allows shell connections, such as Telnet or SSH.
Round Robin mode
A static load balancing mode that bases connection distribution on a set server order. Round Robin mode sends a connection request to the next available server in the order.
A send string is the request that the BIG/ip Controller sends to the web server during an extended content verification (ECV) service check.
A BIG/ip Controller feature that determines whether a node is up or down. When a BIG/ip Controller issues a service check, it attempts to connect to the service hosted by the node. If the connection is successful, the node is up. If the connection fails, the node is down. See also ECV service check, and EAV service check.
SNAT (Secure Network Address Translation)
A SNAT is a feature you can configure on the BIG/ip Controller. A SNAT defines a routable alias IP address that one or more nodes can use as a source IP address when making connections to hosts on the external network.
SNMP (Simple Network Management Protocol)
The Internet standard protocol, defined in STD 15, RFC 1157, developed to manage nodes on an IP network.
sod (switch over daemon)
A daemon that controls the fail-over process in a redundant system.
A controller in a redundant system that is always prepared to become the active unit if the active unit fails.
stateful site content
Content that maintains dynamic information for clients on an individual basis and is commonly found on e-commerce sites. For example, a site that allows a user to fill a shopping cart, leave the site, and then return and purchase the items in the shopping cart at a later time has stateful site content which retains the information for that client's particular shopping cart.
static load balancing modes
Static load balancing modes base connection distribution on a pre-defined list of criteria; it does not take current server performance or current connection load into account.
static site content
A type of site content that is stored in HTML pages, and changes only when an administrator edits the HTML document itself.
A sticky mask is a special IP mask that you can configure on the BIG/ip Controller. This mask optimizes sticky persistence entries by grouping more of them together.
A node that appears as a router to other network devices, including the BIG/ip Controller.
An IP address associated with one or more virtual servers managed by the BIG/ip Controller.
The port number or service name associated with one or more virtual servers managed by the BIG/ip Controller. A virtual port number should be the same TCP or UDP port number to which client programs expect to connect.
A specific combination of a virtual address and virtual port, associated with a content site that is managed by a BIG/ip Controller or other type of host server.
virtual server mapping
The group of nodes across which a virtual server load balances connections for a given site.
watchdog timer card
A hardware device that monitors the BIG/ip Controller for hardware failure.
wildcard virtual server
A virtual server that uses an IP address of 0.0.0.0. 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.