Chapter 11: OSPF Configuration Guide112 SmartSwitch Router User Reference Manual• Type 1 ASE• Type 2 ASEIntra-area paths have destinations within the same area. Inter-area paths havedestinations in other OSPF areas. Both types of Autonomous System External (ASE)routes are routes to destinations external to OSPF (and usually external to the AS). Routesexported into OSPF ASE as type 1 ASE routes are supposed to be from interior gatewayprotocols (e.g., RIP) whose external metrics are directly comparable to OSPF metrics.When a routing decision is being made, OSPF will add the internal cost to the AS borderrouter to the external metric. Type 2 ASEs are used for exterior gateway protocols whosemetrics are not comparable to OSPF metrics. In this case, only the internal OSPF cost to theAS border router is used in the routing decision.The SSR supports the following OSPF functions:• Stub Areas: Definition of stub areas is supported.• Authentication: Simple password and MD5 authentication methods are supportedwithin an area.• Virtual Links: Virtual links are supported.• Route Redistribution: Routes learned via RIP, BGP, or any other sources can beredistributed into OSPF. OSPF routes can be redistributed into RIP or BGP.• Interface Parameters: Parameters that can be configured include interface output cost,retransmission interval, interface transmit delay, router priority, router dead and hellointervals, and authentication key.OSPF MultipathThe SSR also supports OSPF and static Multi-path. If multiple equal-cost OSPF or staticroutes have been defined for any destination, then the SSR “discovers” and uses all ofthem. The SSR will automatically learn up to four equal-cost OSPF or static routes andretain them in its forwarding information base (FIB). The forwarding module then installsflows for these destinations in a round-robin fashion.Configuring OSPFTo configure OSPF on the SSR, you must enable OSPF, create OSPF areas, assign interfacesto OSPF areas, and, if necessary, specify any of the OSPF interface parameters.To configure OSPF, you may need to perform some or all of the following tasks:• Enable OSPF.• Create OSPF areas.• Create an IP interface or assign an IP interface to a VLAN.
