ITPEC FE Morning April 2020 Question 33

Which of the following is an appropriate characteristic of IPv6 addresses?

a)All addresses are global.b)An address consists of 96 bits.c)There are several address representations, one of which uses a hexadecimal string with every four digits (i.e., 16 bits) separated by a colon “:”.d)There is a one-to-one correspondence between all IPv6 addresses and all IPv4 addresses.

Explanation

Hexadecimal groups of four digits separated by colons — an IPv6 address is 128 bits, usually written as eight 16-bit groups such as 2001:0db8:0000:0000:0000:0000:0000:0001.

The same address has several representations: leading zeros in a group may be dropped, and one run of all-zero groups may be replaced by ::, so the example above is also 2001:db8::1.

Answer (c)

Why not others:

•(a) — besides global unicast addresses, IPv6 has link-local (fe80::/10), unique local (fc00::/7), loopback (::1) and multicast addresses
•(b) — an IPv6 address is 128 bits, four times the 32 bits of IPv4, not 96
•(d) — there are 2¹²⁸ IPv6 addresses against 2³² IPv4 addresses, so no one-to-one correspondence is possible; only a small reserved range (IPv4-mapped addresses) embeds IPv4

Key rule: IPv4 = 32 bits in four decimal octets separated by dots; IPv6 = 128 bits in eight hexadecimal 16-bit groups separated by colons.

Networks · AI-written, may contain errors

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