Possible Duplicate:
How does IPv6 subnetting work and how does it differ from IPv4 subnetting?

I have a IPv4-Subnet (/28) and a IPv6-Subnet (/64) - lets say the IPv4 Subnet is "" and the IPv6 one is "2001:1095:10:61::/64" - now I want to give every Server with a IPv4-Address an IPv6 as well. I've heard that it's a good value to do it like this:

Server1: * * 2001:1608:10:61::146

is this possible like this - and would you suggest this way? Whats the greatest number (at the last position) wich is possible?


2 Answers 2


It is possible, and it is used quite frequently, since it makes it easier for admins to remember addresses.

The "biggest number" (counting only the last position) is:

2001:1608:10:61::FFFF # or
2001:1608:10:61::9999 # if you use only decimal numbers in the last quad

The biggest address in your pool is ofcourse:


Depending on what you find to be the "biggest" in your numbering scheme


That is certainly a possible way of numbering your servers. 2001:1095:10:61::/64 contains all addresses from 2001:1095:0010:0061:0000:0000:0000:0000 to 2001:1095:0010:0061:ffff:ffff:ffff:ffff, so 2001:1608:10:61::146 (which is the same as 2001:1608:0010:0061:0000:0000:0000:0146) is possible.

There are many ways to number devices on the network, and the way you describe makes sense if you want to keep IPv4 and IPv6 addresses aligned. I use the same structure in many data centres myself.

  • Thank you very much for you help - now it's more clear! - Only to be sure - after 9999 - it would start with aaaa right?
    – nPoday
    Jan 5, 2013 at 14:32
  • 3
    It's a plain 16-bit hexadecimal number, so after 9999 come 999a, 999b, 999c, ..., 999f, 99a0, etc. Jan 5, 2013 at 15:13

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