Comprehensive and Detailed In-Depth

Infoblox NIOS implements DHCP Failover based on the IETF DHCP Failover protocol (draft standard), using TCP port 647 by default for lease synchronization between peers. This port facilitates the exchange of lease data to ensure both the primary and secondary servers maintain consistent states (e.g., NORMAL, COMMUNICATIONS-INTERRUPTED). TCP is used for reliability, as lease sync requires guaranteed delivery. The port can be changed by the administrator if needed (e.g., for firewall rules), making 'user configured' accurate. Options A and B (port 1194) are incorrect---1194 is commonly associated with OpenVPN, not DHCP Failover. Option D is wrong because it's TCP, not UDP. This is a key DHCP troubleshooting topic in the INE course.