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Q6(d) · Classful and IPv6 addresses
2024-02-06 · AI-only Sem V variant
Exact historical variant. Current-syllabus questions solved; excluded topics and source limitations stated.
Q6(d). I. Find the class of (i)11000011 00111011 00001011 11101111 and (ii)129.5.25.111. II. Distinguish IPv4 and IPv6 addresses. [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.
Step 1. Classify the first octets
11000011₂=128+64+2+1=195: ClassC. 129 lies in128–191: ClassB.
Definition. IPv6 extends address size and reorganizes IP forwarding information into a fixed base header with extension headers.
Simple meaning. Sirf address bada nahi; header ka arrangement bhi badla.
Understand it step by step
- IPv6 uses unicast, multicast and anycast addressing; it does not use IPv4-style broadcast addressing.
- Unicast identifies an interface; multicast addresses a group; anycast reaches one appropriate member of a group sharing an address, according to routing.
- ::1 is loopback. fe80::/10 is link-local space. ff00::/8 identifies multicast. These serve different purposes.
- IPv6 neighbour discovery replaces IPv4 ARP mechanisms. Do not write that IPv6 uses ARP to map its addresses.
- IPv6 is not automatically encrypted or secure merely because it has a larger address space. Security depends on the mechanisms deployed.
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address width | 32 bits | 128 bits |
| Base/header size | 20–60 bytes depending on options | 40-byte fixed base header |
| Length field | Total length includes IPv4 header | Payload Length excludes 40-byte base header |
| Lifetime field | TTL | Hop Limit |
| Following protocol | Protocol field | Next Header; may identify an extension |
| Header checksum | Present | No base-header checksum |
| Options | Inside IPv4 header | Typically extension headers |
| Fragmentation fields | In IPv4 header; routers may fragment if permitted | Fragment extension header; fragmentation by source, not routers |
Yaad rakho: v4 total length; v6 payload length.