IPv6: Creating ranges, range values

Question

So I've just been assigned a /64 IP address range. I'm using SolusVM to manage virtual machines.

With the /64, I am given the first 4 (octets? I think they're called) so my format is currently

XXXX:XXXX:XXXX:XXXX:blank:blank:blank:blank

SolusVM has offered to generate a range of 100 IPs for me. It will only auto-fill the final two octets, so I used:

XXXX:XXXX:XXXX:XXXX:1:1:AUTO:AUTO

and SolusVM generated 100 IPs for me. My question is, how many IPs are there in the XXXX:XXXX:XXXX:XXXX:1:1:AUTO:AUTO range? Assuming that only the values inside the :AUTO:AUTO fields are changeable? Does this have a specific name as a "block" (eg: in place of a /64)

Sorry for the rookie question!

@MichaelHampton: I think the bigger problem might be I'm struggling to get my head around IPv6 properly and what its IPv4 "equivalent" would look like — BnMcG, Dec 01 '15 at 21:14
There isn't an IPv4 "equivalent". Perhaps you should start by reading [this](http://serverfault.com/q/426183/126632). — Michael Hampton, Dec 01 '15 at 21:17
The parts between the colons are definitely not called octets, since they are 16 bits long, not 8. The most common terms seem to be "words" or "quads". — Tilman Schmidt, Dec 02 '15 at 00:56

score 1 · Answer 1 · answered Dec 01 '15 at 21:19

If your provider have only assigned a /64 to you, chances are this is a link prefix. If you have a physical machine on which you want to run many virtual machines, I would recommend getting a shorter routed prefix from your provider (/48 or /56). Then you can split that routed prefix into many /64 which you can use as link prefix on the virtual links between your physical machine and each virtual machine.

If your provider assigned you e.g. 2001:db8:cb61:a389::/64 and your software need to use the entire 2001:db8:cb61:a389:1:1::/96 prefix in order to assign just 100 addresses, it surely isn't using all of that /96. A /96 has 2³² addresses. That's more usable addresses than all of IPv4.

Thanks for this info - I'll read up on it some more. I don't think the software is using the whole of the /96 to assign just 100 addresses, it's just generating 100 at a time instead of 2^32 if that makes sense - I was just curious as to what the maximum amount of IPs would be. — BnMcG, Dec 01 '15 at 21:35

score 1 · Answer 2 · answered Dec 02 '15 at 01:07

Literal answer: The two quads labelled AUTO in your question comprise 2*16 = 32 bits, so the number of distinct addresses you can form that way is 2^32 = 4294967296, all of which can actually be used since there are no reserved ones.

Prudential answer: This is not how IPv6 addressing works. The lower 64 bits are the interface identifier. Only the upper 64 bits are subdivided for subnetting. Either your SolusVM is creating a routed subnet for the VMs in which case you need a bigger address space (shorter prefix) than /64 so that you can give one /64 to SolusVM, or it is bridging the VMs to your network in which case you do not need to care about the address structure at all, just allocate an arbitrary block of addresses to it.

In a SolusVM setup, all the VMs end up bridged together on a single subnet. — Michael Hampton, Dec 02 '15 at 01:37

Jacob Evans · Answer 3 · 2015-12-02T02:54:14.267

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TLDR; XXXX:XXXX:XXXX:XXAA::/64 Where AA = 256 networks (Option B)

You should be asking for a /48, /64 is a 'customer' level subnet, so for home use that's fine but if your plan is to host a bunch of VMs, each VM that a customer could use should be /64.

Also, from an Abuse standpoint /64 is equal to a IPv4/32, and /48 is the equal to an IPv4 /24. (spam/network abuse)

See Cisco's IPv6 subnetting...

edited Dec 02 '15 at 02:54

answered Dec 02 '15 at 02:49

Jacob Evans

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IPv6: Creating ranges, range values

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