A virtual IP address (VIP or VIPA) is an
IP address
An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...
that does not correspond to a physical network interface. Uses for VIPs include
network address translation (especially,
one-to-many NAT), fault-tolerance, and mobility.
Usage
For one-to-many NAT, a VIP address is advertised from the NAT device (often a router), and incoming data packets destined to that VIP address are routed to different actual IP addresses (with address translation). These VIP addresses have several variations and implementation scenarios, including
Common Address Redundancy Protocol
The Common Address Redundancy Protocol or CARP is a computer networking protocol which allows multiple hosts on the same local area network to share a set of IP addresses. Its primary purpose is to provide failover redundancy, especially when used ...
(CARP) and
Proxy ARP
Proxy ARP is a technique by which a proxy server on a given network answers the Address Resolution Protocol (ARP) queries for an IP address that is not on that network. The proxy is aware of the location of the traffic's destination and offers it ...
. In addition, if there are multiple actual IP addresses,
load balancing can be performed as part of NAT.
VIP addresses are also used for connection redundancy by providing alternative fail-over options for one machine. For this to work, the host has to run an interior gateway protocol like
Open Shortest Path First
Open Shortest Path First (OSPF) is a routing protocol for Internet Protocol (IP) networks. It uses a link state routing (LSR) algorithm and falls into the group of interior gateway protocols (IGPs), operating within a single autonomous syst ...
(OSPF), and appear as a router to the rest of the network. It advertises virtual links connected via itself to all of its actual network interfaces. If one network interface fails, normal OSPF topology reconvergence will cause traffic to be sent via another interface.
A VIP address can be used to provide nearly unlimited mobility. For example, if an application has an IP address on a physical subnet, that application can be moved only to a host on that same subnet. VIP addresses can be advertised on their own subnet, so its application can be moved anywhere on the reachable network without changing addresses.
See also
*
Anycast
Anycast is a network addressing and routing methodology in which a single destination IP address is shared by devices (generally servers) in multiple locations. Routers direct packets addressed to this destination to the location nearest the sen ...
, single IP bound simultaneously to many, potentially geographically disparate, NICs
*
IP network multipathing
The IP network multipathing or IPMP is a facility provided by Solaris to provide fault-tolerance and load spreading for network interface cards (NICs). With IPMP, two or more NICs are dedicated for each network to which the host connects. Each int ...
(IPMP),
Solaris virtual IP implementation for fault-tolerance and load balancing
*
VLAN
A virtual local area network (VLAN) is any broadcast domain that is partitioned and isolated in a computer network at the data link layer ( OSI layer 2).IEEE 802.1Q-2011, ''1.4 VLAN aims and benefits'' In this context, virtual, refers to a ph ...
Notes
References
{{DEFAULTSORT:Virtual Ip Address
Cluster computing
IP addresses