IPv6

Agent47

Hey Everyone,
Was taking a practice quiz for the CEH and I came across this question:

Which of the following is a valid IPv6 IP address?

12ED:20:63E2:21BA:0: 3:FACE:F25I

12ED:0:63E2:21BA:0: 3:FACE:F25F

12ED::63E2:21BA:: 3:FACE:F25F

12ED:2F33:63E2:CB24:2D73:FACE:F25F

I have searched a little to get a better understanding of how to tell what is considered valid and im having a little trouble. Could someone help point me in the right direction?

Thanks!

Forsaken_GA

Well the first one is out because of the I in the address. ipv6 is hex based, which is base 16, so all numbers will be 0-9 or A - F. I comes after F, so it's invalid

The third one is out because of the double ::. :: basically means everything between the last digit and the following digit is all 0's, it's a shortcut notation, but it can only occur once within any address.

The fourth one is out because it doesn't have enough bits. Each digit is 4 bits, so each block seperated by a colon is 16 bits. An ipv6 address is 128 bits. The last one has 7 blocks of 16 bits, so it's short 16 bits of being a full address.

That leaves the second one. I'm assuming the space between the : and the 3 is an artifact of your copy/paste, and isn't there in the real example. Spaces aren't valid in ipv6 addresses. ip ipv6, you can omit leading 0's, and identify a single block with just a 0 if you're not using the :: compression method, so the 2nd address has the proper number of bits, doesn't violate the compression rule, and doesn't have any invalid digits.

12ED:0:63E2:21BA:0:3:FACE:F25F would be the proper way to represent the address

ChooseLife

Agent47 wrote: »

Could someone help point me in the right direction?

Do you know the format of IPv6 addresses?
If not, have a quick look here:
IPv6 - Wikipedia, the free encyclopedia

Agent47 wrote: »

12ED:20:63E2:21BA:0: 3:FACE:F25I

Invalid. The address is in Hex, so it cannot have "I" (last symbol)

Agent47 wrote: »

12ED:0:63E2:21BA:0: 3:FACE:F25F

Valid. 8 groups of 16-bit Hex, single colons.

Agent47 wrote: »

12ED::63E2:21BA:: 3:FACE:F25F

Invalid. Only a single double-colon may appear (otherwise it's impossible to establish how many zeroes were omitted in each)

Agent47 wrote: »

12ED:2F33:63E2:CB24:2D73:FACE:F25F

Invalid. Has only 7 groups of 16-bit Hex.

the_hutch

If you register for Hurricane Electric's IPv6 free certification program, it will give you a little hands on experience working with IPv6. Not really a reputable (or verifiable) certification, but its worth doing for a decent learning experience. Hurricane Electric IPv6 Certification

Agent47

Thank you guys so much for your help, I really appreciate it. I'm trying to practice so that I have a better understanding of it and this definitely helps! Hutch, I will do some research on the program as well.