[Kea-users] help with dual stack ddns updates (replacing isc-dhcp with kea-dhcp)

[John Dickinson]

On 16/06/2023 20:23, Bruno Meirelles wrote:

> 2023-06-16T15:44:55.089478-03:00 router kea-dhcp-ddns[6126]: DHCID: 
> [00010161C842CCC250527045EDED24629529B402586F7336E34BF765A1C5D6ECB0B3B5]

> 2023-06-16T15:54:35.615622-03:00 router kea-dhcp-ddns[6126]: DHCID: 
> [000201A4DA3B65FDE300BAE9AD9B667E64199C8F12AA223B3AF1F569C46E640B7BD21F]

It looks like you have different DHCIDs for v4 and v6. They need to 
match so that ddns can see they belong together. See RFC4701 and RFC4361.

The 0001 at the start means that the DHCID is generated from the DHCPv4 
client's Client Identifier option.

The 0002 means that the DHCID is generated from the DHCPv6 DUID.

You can sometimes tell v4 to return a DUID that matches the v6 one but 
how depends on the dhcp client in use. Which is different depending on 
the client OS in use and even what sort of install it is (Ubuntu desktop 
is different from Ubuntu server)!

I tried this a while ago and eventually gave up. I now use static 
addresses pushed in to DNS by ansible. SLAAC to configure v6 addresses 
and ansible scans the zonefile to find free IPv4 addresses. However I 
don't have more than 3 or 4 "dynamic" clients where I care what IP 
address they have.

HTH
John