Is there a way to declare static hosts more smartest?

[Simon Hobson]

On 24 May 2016, at 14:42, Vladimir Skubriev <skubriev at cvisionlab.com> wrote:

> I can't find info what information is stored in txt records. It would be cool if someone suggested ))

It's a hash of various bits of information - including the client and server identity. It's purpose is to make DDNS "safe".

Consider this situation. You have a server which we'll just call "server" for simplicity. A client comes along, and it's user (whether through ignorance or malice) names his client "server". Without some protection, the DHCP server would just update the A and PTR records so that the new client took over the identity of "server" - with "very inconvenient" results for your network.

To avoid this, the DHCP server generates a hash of several bits of information - which includes the identity of the DHCP server. This hash is put in a TXT record for any host it does DDNS for - allowing the server to later confirm that any records it's about to overwrite or delete were actually created by that DHCP server when it was doing updates for a client. If there isn't a matching TXT record, then it won't touch any existing records.

You'll need to look in the DHCP server code to see exactly what information goes in the TXT record, and how the hash is generated.


Had to go looking, but I knew the exact update process had been discussed before
https://lists.isc.org/pipermail/dhcp-users/2006-September/001736.html
Just didn't realise it was quite so long ago.