Enabling OSPF
The easiest and also least scalable way to configure OSPF is to use just a single area. Doing this
requires a minimum of two commands.
The command you use to activate the OSPF routing process is as follows:
Lab_A(config)#router ospf ?
<1-65535>
A value in the range 1–65,535 identifies the OSPF process ID. It’s a unique number on this
router that groups a series of OSPF configuration commands under a specific running process.
Different OSPF routers don’t have to use the same process ID in order to communicate. It’s
purely a local value that essentially has little meaning, but it cannot start at 0. It has to start
at a minimum of 1.