Cisco 3560G 48TS Software Configuration Guide - Page 642

Configuring OSPF Chapter 30 Configuring IP Unicast Routing • Default route: When you specifically configure redistribution of routes into an OSPF routing domain, the route automatically becomes an autonomous system boundary router (ASBR). You can force the ASBR to generate a default route into the OSPF routing domain. • Domain Name Server (DNS) names for use in all OSPF show privileged EXEC command displays makes it easier to identify a router than displaying it by router ID or neighbor ID. • Default Metrics: OSPF calculates the OSPF metric for an interface according to the bandwidth of the interface. The metric is calculated as ref-bw divided by bandwidth, where ref is 10 by default, and bandwidth (bw) is determined by the bandwidth interface configuration command. For multiple links with high bandwidth, you can specify a larger number to differentiate the cost on those links. • Administrative distance is a rating of the trustworthiness of a routing information source, an integer between 0 and 255, with a higher value meaning a lower trust rating. An administrative distance of 255 means the routing information source cannot be trusted at all and should be ignored. OSPF uses three different administrative distances: routes within an area (interarea), routes to another area (interarea), and routes from another routing domain learned through redistribution (external). You can change any of the distance values. • Passive interfaces: Because interfaces between two devices on an Ethernet represent only one network segment, to prevent OSPF from sending hello packets for the sending interface, you must configure the sending device to be a passive interface. Both devices can identify each other through the hello packet for the receiving interface. • Route calculation timers: You can configure the delay time between when OSPF receives a topology change and when it starts the shortest path first (SPF) calculation and the hold time between two SPF calculations. • Log neighbor changes: You can configure the router to send a syslog message when an OSPF neighbor state changes, providing a high-level view of changes in the router. Beginning in privileged EXEC mode, follow these steps to configure these OSPF parameters: Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Step 8 Step 9 Command Purpose configure terminal Enter global configuration mode. router ospf process-id Enable OSPF routing, and enter router configuration mode. summary-address address mask (Optional) Specify an address and IP subnet mask for redistributed routes so that only one summary route is advertised. area area-id virtual-link router-id [hello-interval seconds] [retransmit-interval seconds] [trans] [[authentication-key key] | message-digest-key keyid md5 key]] (Optional) Establish a virtual link and set its parameters. See the "Configuring OSPF Interfaces" section on page 30-31 for parameter definitions and Table 30-6 on page 30-29 for virtual link defaults. default-information originate [always] [metric metric-value] [metric-type type-value] [route-map map-name] (Optional) Force the ASBR to generate a default route into the OSPF routing domain. Parameters are all optional. ip ospf name-lookup (Optional) Configure DNS name lookup. The default is disabled. ip auto-cost reference-bandwidth ref-bw (Optional) Specify an address range for which a single route will be advertised. Use this command only with area border routers. distance ospf {[inter-area dist1] [inter-area (Optional) Change the OSPF distance values. The default distance dist2] [external dist3]} for each type of route is 110. The range is 1 to 255. passive-interface type number (Optional) Suppress the sending of hello packets through the specified interface. 30-34 Catalyst 3560 Switch Software Configuration Guide 78-16156-01