Computer Networks · TEE · papers
Q1(c) · Classful addressing
2023-11-22 · Final 2023-24 / Re-exam 2022-23
Actual paper; 100 marks attempted. Current-syllabus alignment is stated per question.
Q1(c). Explain the significance of IP addressing in computer networks. Illustrate the classfull addressing scheme in computer networks, with address range and default subnet mask of each class. [5 marks]
Answer
An IPv4 address identifies an IP interface. The network prefix selects the destination network; remaining bits identify an address within it. Classful addressing is historical; modern routing uses explicit CIDR prefixes.
| Class | First octet | Default mask | Network / host split | Purpose |
|---|---|---|---|---|
| A | 1–126 (ordinary unicast) | 255.0.0.0 (/8) | 8 / 24 bits | Large historical unicast networks; 0 and 127 reserved |
| B | 128–191 | 255.255.0.0 (/16) | 16 / 16 bits | Medium historical unicast networks |
| C | 192–223 | 255.255.255.0 (/24) | 24 / 8 bits | Small historical unicast networks |
| D | 224–239 | No unicast default mask | Not network/host class split | Multicast |
| E | 240–255 | No unicast default mask | Not normal unicast allocation | Reserved/experimental; special addresses exist |
Example: 114.34.2.8 is class A with network 114.0.0.0 and host portion 34.2.8. Class does not override an explicitly supplied CIDR prefix.