OSPF Topology Database
• OSPF topology database consists of:
• Subnet numbers or ‘links’ with ‘cost’.
• Unique Router ID
• A Cisco router uses the following criteria to select RID:
• The router first looks for the existence of any loopback interfaces
that are up. If so, the router picks the highest numeric IP address
among the loopback interfaces.
• If no loopback is found, the router picks the highest numeric IP
address from all its working (up and up) interfaces.