IP Standards and Public and Private Addresses

Overview

Recall questions on the two current standards, the format of each, how many addresses each provides and the private address ranges.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What are the two current standards of IP address?

   Model answer

   Version 4 and version 6.

2. 2

   Describe the format of a version 4 IP address.

   Model answer

   A version 4 address is 32 bits long. It is normally written as four decimal numbers separated by full stops, one for each 8-bit octet, each therefore in the range 0 to 255 — for example 192.168.0.1.

3. 3

   Describe the format of a version 6 IP address.

   Model answer

   A version 6 address is 128 bits long. It is written as eight groups of four hexadecimal digits separated by colons, with rules allowing leading zeros within a group to be dropped and one run of all-zero groups to be replaced by a double colon to shorten it.

4. 4

   How many addresses does each standard provide?

   Model answer

   Version 4 has 32 bits, giving 2³² addresses, which is about 4.3 billion — 4,294,967,296 exactly, and fewer than that once reserved ranges are taken out. Version 6 has 128 bits, giving 2¹²⁸ addresses, a number vastly larger than the version 4 space and far beyond any foreseeable need.

5. 5

   Explain why version 6 was introduced.

   Model answer

   Chiefly because the version 4 address space was running out. Around 4.3 billion addresses seemed limitless when the standard was designed, but the growth of the Internet, and then the arrival of smartphones and of large numbers of internet-connected devices per household, meant the unallocated blocks were exhausted. Version 6's 128-bit addresses remove the shortage permanently. Its introduction also allowed other improvements: a simplified header that routers can process more quickly, built-in support for encryption and authentication, and automatic address configuration without needing a separate server.

6. 6

   If version 6 fixes the address shortage, why is version 4 still in widespread use?

   Model answer

   Because the change requires every router, operating system and application on the path to support the new standard, and the two are not directly interoperable, so the transition has to be gradual with both running side by side. Meanwhile techniques such as private addressing with address translation have stretched the version 4 space far enough that the pressure to convert has been reduced, which has slowed adoption further.

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