Netgear FSM726v3 7000 Series Managed Switch Administration Guide for Software - Page 106

Chapter 8 OSPF In this chapter, the following examples are provided: • "Configure an Inter-Area Router" on page 8-2 • "Configure OSPF on a Border Router" on page 8-8 • "Configure Area 1 as a Stub Area" on page 8-15 • "Configure Area 1 as a nssa Area" on page 8-24 • "VLAN Routing OSPF Configuration" on page 8-35 • "OSPFv3 (Open Shortest Path First)" on page 8-40 For larger networks Open Shortest Path First (OSPF) is generally used in preference to RIP. OSPF offers several benefits to the administrator of a large and/or complex network: • Less network traffic: - Routing table updates are sent only when a change has occurred - Only the part of the table which has changed is sent - Updates are sent to a multicast, not a broadcast, address • Hierarchical management, allowing the network to be subdivided The top level of the hierarchy of an OSPF network is known as an autonomous system (AS) or routing domain, and is a collection of networks with a common administration and routing strategy. The AS is divided into areas: intra-area routing is used when a source and destination address are in the same area, and inter-area routing across an OSPF backbone is used when they are not. An inter-area router communicates with border routers in each of the areas to which it provides connectivity. The 7000 Series Managed Switch operating as a router and running OSPF will determine the best route using the assigned cost and the type of the OSPF route. The order for choosing a route if more than one type of route exists is as follows: • Intra-area • Inter-area • External type 1: the route is external to the AS • External Type 2: the route was learned from other protocols such as RIP 8-1 v1.0, October 2009