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I was reading about 6to4 and I'm pretty confused about how the addresing works.

If you are converting an IPv4 to IPv6 using 6to4 first group will be 2002

The next groups are determined by the IPv4 address, for example

192.168.200.1 255.255.0.0

So would the next 2 groups be derived from the network address of 192.168.0.0 or from the actual 192.168.200.1 ?

I am also confused about the role of the subnet id, do I include it right after the 32 bit address?

network address -> 2002:C0A8:0000:subnetid::

actual addres -> 2002:C0A8:C801::/48

Help much appreciated!

ewakwwg12
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  • I maybe misunderstood your question. But in 6to4 the prefix has 48 Bits (from a 32Bit iPv4). 16 Bits for the Subnet and 64 Bits for the host. – SickerDude43 Feb 24 '23 at 17:43
  • @SickerDude43 Is the Subnet a separate address kind of like 255.255.0.0 ? My impression was the Subnet ID is a part of the IPv6 address scheme – ewakwwg12 Feb 24 '23 at 17:49
  • Kinda.. The subnet mask is a bitmask. It results that you have more than the "standard" 255 subnet adresses. – SickerDude43 Feb 24 '23 at 18:56

1 Answers1

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Example

That's how an IPv6 is built. You start with the Site Prefix, follow with the Subnet ID and end with the Interface ID.

6to4 works on the prefix. There's a great example on Wikipedia:

6to4

As you can see, from the 32Bit IPv4 a new IPv6 was constructed which has the length of 48 Bits. The two : at the end are like placeholders. After the first one you can fit in the Subnet ID[16Bit]. After the second one there is place for the Interface(or Host) ID [64Bit]. Together they equal 128 Bits, not 112. Basically the newly constructed Prefix from the second image (2002:c000:0204) is the Site Prefix in the image above. The convertion only happens on the Prefix.

Sources: https://docs.oracle.com/cd/E23823_01/html/816-4554/ipv6-overview-10.html

https://wikipedia.org/wiki/6to4

SickerDude43
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