When you change the native VLAN of a trunk from VLAN 1 to VLAN 999 and you receive the error
%CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered…,
what is the possible problem?

A. CDP is not running on the other interface, causing a mismatch.
B. The interface is the first to be changed.
C. The interface is running ISL.
D. The version of CDP is wrong on the other switch.

B. This error is normal if it is the first interface to be changed over to the new native VLAN since the other interface has not been changed yet. However, if the other interface was changed already and you received this error, then CDP is letting you know that the other side is mismatched.