question In IPv6, are "fd" and "fc" acronyms? Do they stand for anything in particular?

[Halgorithm]

I looked it up online but honestly couldn't find an answer. Are there any other existing prefixes for IPv6 addresses? If so, what do those ones stand for? 

Thanks! 

 

[Lurick]

Nope, just towards the end of the IPv6 address range to stay away from usable space.

fc00::/8 is for unique local and assigned from say a DHCP or other provider server but beyond that it's not routable on the internet

fd00::/8 is only for a locally assigned (IE fd00:: + 40 random bits) without a provider of some kind to generate/hand out addresses. Also not routable

fe80::/10 is for link local addresses only.

ff00::/8 is for multicast

 

Edit:

Ripe has a good breakout and equivalent mapping as well:

https://www.ripe.net/participate/member-support/lir-basics/ipv6_reference_card.pdf

[Halgorithm]

17 minutes ago, Lurick said:

Nope, just towards the end of the IPv6 address range to stay away from usable space.

fc00::/8 is for unique local and assigned from say a DHCP or other provider server but beyond that it's not routable on the internet

fd00::/8 is only for a locally assigned (IE fd00:: + 40 random bits) without a provider of some kind to generate/hand out addresses. Also not routable

fe80::/10 is for link local addresses only.

ff00::/8 is for multicast

 

Edit:

Ripe has a good breakout and equivalent mapping as well:

https://www.ripe.net/participate/member-support/lir-basics/ipv6_reference_card.pdf

Thanks for your answer, I really appreciate it!
I understood most of your explanation, except in the 1st part when you refer to "usable space". What do you mean by "to stay away from usable space"?

[Alex Atkin UK]

5 minutes ago, Halgorithm said:

Thanks for your answer, I really appreciate it!
I understood most of your explanation, except in the 1st part when you refer to "usable space". What do you mean by "to stay away from usable space"?

Its designed to not conflict with normal public routable IPs.  Its just an allocation for other purposes than normal routable IP addresses.

 

Remember, IPv6 is designed around the whole world being one big IPv6 network that every single device can talk to each other directly.  So we still needed a way to define a local-only private LAN for certain traffic.

[Lurick]

11 minutes ago, Halgorithm said:

Thanks for your answer, I really appreciate it!
I understood most of your explanation, except in the 1st part when you refer to "usable space". What do you mean by "to stay away from usable space"?

Well the current usable block for IPv6 is 2000::/3 so not having to carve out blocks in the middle of that space later on for some reason was the goal. IPv6 goes from ::1/128 to all f's so having addresses that aren't routable as far to one side of that range as possible makes subnetting simpler