A. Determine that the backbone area will not split.

B. Check whether secondary optimal routes exist on the network according to OSPF route selection rules.

C. Check whether all non-backbone areas are correctly and reliably connected to the backbone area.

D. Verify that OSPF costs can correctly demonstrate the actual bandwidth of links at more than 100 Mbit/ s.

E. Check the OSPF network topology and ensure that no loop exists when OSPF routes are being calculated.