IPv6 Prefix ID Selection

Hey there,
I own a Fritzbox and use the manual update-URL with success.
The delegated /56 prefix and the ipv4 gets update regulartly.

My problem is, that the /56 is delegated to other routers. So I want to update the ipv6-prefix of the zone to lets say the /64-prefix out of the /56-prefix with the id 4.

I couldn’t find this feature so is that possible or not?

If that would be possible this service would be what I was looking for so long! I got it working by using a Server inside the ID 4 prefix and updating the prefix that way. But thats more like a workaround, because I like it more when it gets managed by the router which gets the prefix in the first place.

Best regards

That’s a feature dynv6 supports! If the first 6 octets of the IPv6 address of the AAAA record are zero, our DNS server adds the first 8 octets of the prefix to the IPv6 address (bitwise OR). Example:

  • 2001:dead:beef:200::/56 + ::4:a:b:c:d => 2001:dead:beef:204:a:b:c:d

Our source code written in Go:

var ip, prefix net.IP
// ...
if ip[0] == 0 && ip[1] == 0 && ip[2] == 0 && ip[3] == 0 && ip[4] == 0 && ip[5] == 0 {
	for i := 0; i < 8; i++ {
		ip[i] |= prefix[i]
1 Like

Can you pls say me How you Mean it the first 6 Octets

One octet is equivalent to two hexadecimals: 0x00 - 0xFF

so the first octet in the example above is 0x20
the second is 0x01
the third is 0xDE
and so on…