You work as network administrator at TestKing  
Your trainee is configuring a router with both physical and logical interfaces.  
He asks you what factor determines the OSPF router ID.  
What should you tell him?  
A. The lowest network number of any interface.  
B. The lowest IP address of any logical interface.  
C. The lowest IP address of any physical interface.  
D. The highest network number of any interface.  
E. The highest IP address of any logical interface.  
F. The highest IP address of any physical interface.  
Answer: F  

Explanation:  

The OSPF topology database includes information about routers and the subnets, or links, to which they are attached. To identify the routers in the neighbor table’s topology database, OSPF uses a router ID (RID) for each router. A router’s OSPF RID is that router’s highest IP address on a physical interface when OSPF starts  running.