Civil Aviation Authority of Nepal2077 BSQuestion 9 of 18
What is IP address? Discuss different classes of IPV4 addresses and quantify the number of networks and hosts in each class of the network. Explain the role of a gateway in a network.
10 marks
Question source
- Exam year
- 2077 BS / 2021 AD
- Level
- Level 5 (Prabidhik, IT, Barishtha Sahayak)
- Paper
- Paper II – Sewa Sambandhi
- Section
- Section A
Model answer
An IP address uniquely identifies a device on a network. IPv4 is 32-bit, written as 4 decimals (e.g. 192.168.1.10).
IPv4 classes (first octet decides):
| Class | Range | Networks | Hosts per net | Use |
|---|---|---|---|---|
| A | 1–126 | 126 (2⁷−2) | ~16M (2²⁴−2) | Huge orgs/ISPs |
| B | 128–191 | ~16k (2¹⁴) | ~65k (2¹⁶−2) | Universities, large offices |
| C | 192–223 | ~2M (2²¹) | 254 (2⁸−2) | Small LANs — most Nepal offices |
| D | 224–239 | — | — | Multicast (video), not host addressing |
| E | 240–255 | — | — | Experimental/reserved |
Minus 2 for network and broadcast addresses. Private ranges (never on internet): 10.x.x.x, 172.16–31.x.x, 192.168.x.x.
Gateway role: Router IP (e.g. 192.168.1.1) linking LAN to other networks/internet. PC sends outside-bound packets to gateway, which forwards them. Wrong gateway = "connected but no browsing".