Computer Networks · TEE · practice

DHCP timer example 1

ARP, RARP and DHCP · optional practice

Optional extension · no matching calculation in the two supplied papers

Optional worked extension. This calculation format was not found in the supplied December 2025 final or February 2026 re-exam. The numbers and practice marks are authored. Study the core concept and actual-paper questions first; this is extra explanation, not a TEE prediction.

Practice question. A DHCPv4 lease lasts 8 hours. No different T1 or T2 values are supplied. Find the default renewal and rebinding times after lease acquisition. [3 practice marks]

Answer

Given

Lease duration L=8 h; use default fractional timers.

To find

T1 and T2 as elapsed times.

Formula and why

T_1=0.5L,\qquad T_2=0.875L

Use these defaults only when the server/question has not specified other timer values.

Step-by-step solution

Step 1. Renewal timer

T1=0.5×8=4 h.

Step 2. Rebinding timer

T2=0.875×8=7 h.

Step 3. Place them before expiry

4 h < 7 h < 8 h.

Final answer: T1=4 h; T2=7 h.