<div dir="ltr">Thank you for detailed answer.<div><br></div><div>I fully agree with you about the security<br></div><div><br></div><div>I understand about what is stored in it.<br></div><div><br></div><div>But I still do not like the DDNS ))<br></div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">2016-05-24 17:28 GMT+03:00 Simon Hobson <span dir="ltr"><<a href="mailto:dhcp1@thehobsons.co.uk" target="_blank">dhcp1@thehobsons.co.uk</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=""><br>
On 24 May 2016, at 14:42, Vladimir Skubriev <<a href="mailto:skubriev@cvisionlab.com">skubriev@cvisionlab.com</a>> wrote:<br>
<br>
> I can't find info what information is stored in txt records. It would be cool if someone suggested ))<br>
<br>
</span>It's a hash of various bits of information - including the client and server identity. It's purpose is to make DDNS "safe".<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.<br>
<br>
<br>
Had to go looking, but I knew the exact update process had been discussed before<br>
<a href="https://lists.isc.org/pipermail/dhcp-users/2006-September/001736.html" rel="noreferrer" target="_blank">https://lists.isc.org/pipermail/dhcp-users/2006-September/001736.html</a><br>
Just didn't realise it was quite so long ago.<br>
<div class="HOEnZb"><div class="h5"><br>
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</div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div>Faithfully yours,<br></div><div><br></div><div>CVision Lab System Administrator</div><div>Vladimir Skubriev</div><div><br></div></div></div>
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