CISCO CCNA 200-301 Q148

Which of the following are NOT valid IPv6 addresses? (Choose all that apply.)

B. ::FFFF:
C. ::
D. 2001:0:42:3:ff::1
E. fe80:2030:31:24
F. 2001:42:4:0:0:1:34:0
G. 2003:dead:beef:4dad:ab33:46:abab:62

Correct Answer: A, E

The addresses and fe80:2030:31:24 are not valid IPv6 addresses. is incorrect because it is an IPv4 multicast address. The address fe80:2030:31:24 is incorrect because it does not represent a 16-byte IPv6 address, with colons separating each 2-byte segment.

IPv6 addresses are 16 bytes, or 128 bits in length. The following are valid IPv6 addresses.

::FFFF: is an example of an IPv4-compatible IPv6 address, where the first 10 bytes (80 bits) of the address are set to 0 the next 2 bytes (16 bits) are set to FFFF and the last 32 bits are the IPv4 address

:: is the IPv6 “unspecified address.” It is a unicast address not assigned to any interface, and is used by a DHCP-dependent host prior to allocating a real IPv6 address.

2001:0:42:3:ff::1 is a valid IP address, with the :: representing two segments (4 bytes) of compressed zeros.

2001:42:4:0:0:1:34:0 is a valid IP address, with only the leading zeros of each segment truncated.

2003:dead:beef:4dad:ab33:46:abab:62 has 16 bytes, is divided correctly by colons into eight sections, utilizes the dropping of leading zeros in each section correctly, and uses the letters a-f in the three section that spell out dead beef 4 dad.