- Multi-Tech User Guide Modem MTASR1-100

Chapter 4 - RouteFinder Software
MTASR1-100 31
Open Shortest Path First (OSPF)
Open Shortest Path First (OSPF) is a common TCP/IP routing protocol that provides robust and
efficient routing support in the most demanding Internet environments. OSPF calculates routes using
the number of routers, the transmission speed, expected delays, and the cost of the route. Version 2
of the OSPF protocol is designed to be run internal to a single Autonomous System. Each OSPF
router maintains an identical database describing the topology of the Autonomous System. From this
database, a routing table is calculated by constructing a “shortest-path” tree.
OSPF recalculates routes quickly in the event of topological changes, using a minimum of routing
protocol traffic.
Under OSPF, networks can be grouped together into “areas,” each of which is the generalization of an
IP subnetted network. The topology of an area is hidden from the rest of the Autonomous System, and
this information hiding enables a significant reduction in routing traffic. Also, routing within an area is
determined only by the area’s own topology, protecting the area from “bad” routing data.
All OSPF protocol exchanges are authenticated; i.e., only trusted routers can participate in the
Autonomous System’s routing. Furthermore, a variety of authentication schemes can be used; in fact,
separate authentication schemes can be configured for each IP subnet.
Clicking the OSPF button on the Advanced tab opens the General Setup dialog box.