HSIM-W6 Firmware Support
HSIM-W6 Installation Guide
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OSPF, based upon link-state technology, was developed by the Internet Engineering Task Force
(IETF). The IETF developed OSPF based upon the shortest path first algorithm to serve large,
heterogeneous networks.
A key feature of OSPF is the speed in which it responds to topological changes, commonly
referred to as “convergence time.” OSPF generates a minimal amount of routing protocol traffic
compared to most distance vector protocols.
Cabletron’s implementation of OSPF is based on RFC 1247 — OSPF Version 2 and RFC 1253 —
OSPF Version 2 Management Information Base.
IP-OSPF Hierarchy
IP-OSPF operates within a hierarchy of entities:
Autonomous System
An Autonomous System (AS) is a set of routers and networks under a common administration.
Routers inside an AS are called “interior gateways” and the protocol is called Interior Gateway
Protocol (IGP). OSPF is an IGP.
Every OSPF routing domain must have a backbone. An OSPF backbone distributes routing
information between areas in an OSPF routing domain. The backbone of an OSPF routing domain
system is an OSPF area possessing an area id of 0.0.0.0.
Areas
Areas are groups of networks and attached hosts. A router’s topology database includes area links,
and summarized and external links depicting the autonomous system topology. From this
database, routers calculate a route using the shortest-path tree algorithm.
The Hello Protocol
The Hello Protocol establishes and maintains neighbor relationships, and ensures bidirectional
communications among neighboring routers. Hello packets are sent out all router ports
periodically. A designated router is chosen by the Hello Protocol on multi-access networks and
controls adjacencies formed over the network.
Neighbors and Adjacency
The OSPF routing protocol establishes adjacencies among neighboring routers which facilitate the
exchange of routing information. Neighboring routers have interfaces to a common network and
are discovered by OSPF’s Hello Protocol.
