Introduction
Open Shortest Path First (OSPF) is a routing protocol for IP. It is a link-state protocol, as opposed to a distance-vector protocol. A link-state protocol makes routing decisions based on the states of the links that connect source and destination machines. The state of a link is a description of that interface and the relationship to its neighboring networking devices. The interface information includes the IPv6 prefix of the interface, the network mask, the type of network it is connected to, the routers connected to that network, and so forth. This information is propagated in various type of link-state advertisements (LSAs).
OSPF version 3, which is described in RFC 2740, supports IPv6.
Open Shortest Path First (OSPF) is a routing protocol for IP networks. It is used inside an organization’s routing domain, making it an interior protocol, as opposed to being used between the organization’s network and other networks (edge routing, done with edge protocols). Other interior routing protocols include Intermediate System-to-Intermediate System (IS-IS) and Enhanced Interior Gateway Routing Protocol (EIGRP).
OSPF routers create a routing table showing the shortest-path routes through the network. When a component fails, the routers automatically reroute around it. Routers build these tables based on their link state database, which they populate based on link state advertisements (LSAs) from other routers in the network. LSAs are the means by which the network maintains its current knowledge about routing traffic.
How OSPFv3 Works
OSPFv3 is a routing protocol for IPv4 and IPv6. It is a link-state protocol, as opposed to a distance-vector protocol. Think of a link as being an interface on a networking device. A link-state protocol makes its routing decisions based on the states of the links that connect source and destination machines. The state of a link is a description of that interface and its relationship to its neighboring networking devices. The interface information includes the IPv6 prefix of the interface, the network mask, the type of network it is connected to, the devices connected to that network, and so on. This information is propagated in various type of link-state advertisements (LSAs).
A device’s collection of LSA data is stored in a link-state database. The contents of the database, when subjected to the Dijkstra algorithm, result in the creation of the OSPF routing table. The difference between the database and the routing table is that the database contains a complete collection of raw data; the routing table contains a list of shortest paths to known destinations via specific device interface ports.
OSPFv3, which is described in RFC 5340, supports IPv6 and IPv4 unicast AFs.
