Which misconfiguration would cause an OSPF neighborship to be stuck in an ExStart state?

A.
authentication mismatch

B.
timer mismatch

C.
subnet mismatch

D.
MTU mismatch

Explanation:
Summary:
What is the MTU value used by OSPF when Jumbo Frames are enabled in high-end firewalls?

Problem or Goal:
Cannot establish OSPF neighborship because of OSPF MTU Mismatch; they are stuck in Exstart/Exchange State.
Solution:
When Jumbo Frames are enabled, ScreenOS will modify the maximum frame size per system and IP MTU on all interfaces. The IP MTU is used by OSPF and it cannot be set per interface. The formula for calculating the IP MTU is as follows:
IP MTU (used by OSPF) = max-frame-size – Ethernet Header Length (14 bytes)
For example:
If max-frame-size = 9830, then the IP MTU = 9816.

Solution 1
Make sure to have the same IP MTU on both ends.

Solution 2
Ignore any mismatches in Maximum Transmission Unit (MTU) values between the local and remote interfaces found during OSPF database negotiations. The following option should only be used when the MTU on the local interface is lower than the MTU on the remote interface:
set interface <interface> protocol ospf ignore-mtu