LISP (Location Identifier Separation Protocol) is a routing and addressing architecture developed by Cisco Systems.
LISP creates two addresses for each network node: one for its identity and another for its location in the network. This approach contrasts with the traditional practice of using a single numbered address -- an IP address -- to represent both identity and location. LISP was designed to help scale Internet routing tables, which have expanded aggressively over the years and will continue to grow more complex as IPv6 adoption continues.
LISP addresses are respectively known as Endpoint Identifiers (EIDs) and the Routing Locators (RLOCs). Each node on the network has one Endpoint Identifier but may have multiple and variable Routing Locators. The protocol provides a mapping service between them.
With traditional addressing architectures, a device needs a new IP address each time it changes networks. Therefore, if a tablet user switches network connectivity from 4G to Wi-Fi, or a virtual machine (VM) is migrated to another physical server in the data center, the device or object requires a new IP address. In the data center scenario, assigning a migrated VM a new IP address means that all other services attached to the VM -- firewalls, load balancers and so forth -- won't be able to "find" the VM until an administrator re-configures them with the new address. LISP allows a node to keep the same IP address even when its location changes because it keeps its EID while mapping to multiple RLOCs. LISP-enabled edge routers can aggregate EID prefixes with closely aligned RLOCs, making it easier for a core router to quickly determine where to send data.
Cisco created LISP and has led its development in the IETF's LISP Working Group since its formation in 2009, but the company has stated it claims no intellectual property rights and that LISP is being developed as an open standard. The protocol's other benefits include improved multi-homing and traffic engineering.
Jimmy Ray Purser explains the benefits of LISP in the real world.