Computer Networks · TEE · read

Exact route aggregation · example 1

CIDR, VLSM and route matching

TEE · shared foundations and Units 3–4 · current syllabus 702AI0C023

Practice question. Find a single exact CIDR aggregate for these networks: 192.168.4.0/24, 192.168.5.0/24, 192.168.6.0/24, 192.168.7.0/24. [3 practice marks]

Answer

Given

  • 192.168.4.0/24
  • 192.168.5.0/24
  • 192.168.6.0/24
  • 192.168.7.0/24

To find

One prefix covering exactly the same address range.

Formula and why

\text{total addresses}=\sum_i N_iLaTeX: \text{total addresses}=\sum_i N_i
p=32-\log_2(N)LaTeX: p=32-\log_2(N)

Adding sizes gives the candidate prefix. Contiguity and start-boundary alignment must also be satisfied.

Step-by-step solution

Step 1. Determine each block size

Each input block has 256 addresses.

Step 2. Add the address counts

4×256=1024.

Step 3. Find host bits and prefix

1024=210; prefix=32−10=/22.

Step 4. Verify the exact range

Inputs cover 192.168.4.0–192.168.7.255, without gaps. 192.168.4.0/22 covers the same start and end and is correctly aligned.

Final answer: 192.168.4.0/22