What are two reasons that will prevent two routers from forming an OSPFv2 adjacency? (Choose two.)

What are two reasons that will prevent two routers from forming an OSPFv2 adjacency? (Choose two.)

• a mismatched Cisco IOS version that is used
• mismatched OSPF Hello or Dead timers
• mismatched subnet masks on the link interfaces
• use of private IP addresses on the link interfaces
• one router connecting to a FastEthernet port on the switch and the other connecting to a GigabitEthernet port

Explanation: There may be several reasons why two routers running OSPF will fail to form an OSPF adjacency, including these:
The subnet masks do not match, causing the routers to be on separate networks.
OSPF Hello or Dead Timers do not match.
OSPF network types do not match.
There is a missing or incorrect OSPF network command.
Mismatched IOS versions, the use of private IP addresses, and different types of interface ports used on a switch are not causes for an OSPF adjacency failing to form between two routers.

Exam with this question: CCNA 3 (v5.0.3 + v6.0) Chapter 8 Exam Answers
Exam with this question: CCNA 2 (v5.0.3 + v6.0) Chapter 8 Exam Answers
Exam with this question: CCNP Enterprise: Advanced Routing (Version 8.0) – OSPF Exam