| OSPF | ||
| Hello/dead time | 10/40, | 30/1 20 |
| Cisco or IETF | I ETF | |
| Updates | Multicast (224.0.0.5, 224.0.0.6) | |
| Load balancing | Equal paths | |
| Routed protocols | IP | |
| OSPF | ||
| Hello/dead time | 10/40, | 30/1 20 |
| Cisco or IETF | I ETF | |
| Updates | Multicast (224.0.0.5, 224.0.0.6) | |
| Load balancing | Equal paths | |
| Routed protocols | IP | |
OSPF is a link-state routing protocol that automatically discovers its neighbors by sending hello messages to 224.0.0.5. After the neighbors are discovered, they form an adjacency by synchronizing their databases. This database lists all possible routes that the neighbor is aware ofin the topology. Each subnet learned has a cost associated with it, which is calculated by taking 1 08/bandwidth. The paths with the lowest cost to a destination are put in the routing table.
| TCost Values Based on Bandwidth | |
| Bandwidth | OSPF Cost |
| 56Kbps | 1785 |
| 64Kbps | 1562 |
| T1 (1 .544 Mbps) | 64 |
| E1 (2048 Mbps) | 48 |
| Ethernet (10 Mbps) | 10 |
| Fast Ethernet (100 Mbps)Gigabit Ethernet (1000 Mbps) | 11 |
Verifying and Troubleshooting OSPF Commands
| Command | Output |
| show ip route | The routing table with OSPF entries represented as “O.” Routes learned from other areas also have an interarea indicator ( “ IA”). |
| show ip protocols | OSPF process ID and advertised networks. |
| show ip ospf interface | Local router’s router ID, interface topology type, link cost and priority, router ID for the DR and BDR on the segment, hello/dead intervals, and a count of how many neighbors and adjacencies. |
| show ip ospf neighbor | Neighbor table to verify neighbor IDs and if neighbor is DR or BDR. |
| showip ospf database | OSPF subnets and advertising routers in the topology table. |
| debug ip ospf events | Real-time display of LSAs and LSUs being sent and received. |