Which three statements are true regarding the OSPF router ID? (Choose three.)
A.
The OSPF routing process chooses a router ID for itself when it starts up.
B.
The router-id command is the preferred procedure to set the router ID.
C.
If a loopback interface is configured, its address will always be preferred as the router ID over
any other methods.
D.
After the router ID is set, it does not change, even if the interface that the router is using for the
router ID goes down. The router ID changes only if the router reloads or if the OSPF routing
process restarts.
E.
In OSPF version 3, the OSPF router ID uses a 128-bit number.
Explanation:
http://wiki.nil.com/OSPF_Router_ID_selection_algorithm