CISCO CCNA Exam – Q243

How does a DHCP server dynamically assign IP addresses to hosts?

A. Addresses are permanently assigned so that the host uses the same address at all times.
B. Addresses are assigned for a fixed period of time. At the end of the period, a new request for an address must be made, and another address is then assigned.
C. Addresses are leased to hosts. A host will usually keep the same address by periodically contacting the DHCP server to renew the lease.
D. Addresses are allocated after a negotiation between the server and the host to determine the length of the agreement.

Correct Answer: C

DHCP works in a client/server mode and operates like any other client/server relationship. When a PC connects to a DHCP server, the server assigns or leases an IP address to that PC. The PC connects to the network with that leased IP address until the lease expires. The host must contact the DHCP server periodically to extend the lease. This lease mechanism ensures that hosts that move or power off do not hold onto addresses that they do not need. The DHCP server returns these addresses to the address pool and reallocates them as necessary.