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<p>Hi all, <br>
</p>
<p>I sent this email few weeks ago (without being subscribed
here), and didn't receive any reply, nor do I see it in lists
archive. So I write once again after subscription, hope it
will work now.<br>
</p>
<p>~~~~<br>
</p>
<p>My isc dhcp server behaves strangely - it sends some clients
dhcp hostname option value which I don't know where it is
getting it from.</p>
<p>It's on Debian 8.5, version 4.3.1. It's in failover mode.</p>
<p>I'm using dynamic hostname generation for some clients based
on last byte of their mac address:</p>
<pre><code>set mac_6 = suffix(concat("0", binary-to-ascii(16, 8, "", substring(hardware, 6, 1))), 2);
ddns-hostname = concat("vm1", mac_6);
option host-name = config-option server.ddns-hostname;
</code></pre>
<p>So for example client with mac address ending 02 should get
hostname vm102 - and it seems to work correctly - I added
logging to my dhcp config and I see in log file both option
host-name and config-option server.ddns-hostname set to vm102.
</p>
<p>I also see in dhcpd.leases </p>
<pre><code>set mac_6 = "02";
client-hostname "vm102";
</code></pre>
<p>But when I run tcpdump for this client, I see</p>
<p><code>Hostname Option 12, length 5: "vm121" </code></p>
<p>and at least once it changed to vm103.</p>
<p>So where is it getting it from? What are the sources for this
option when dhcp server sends DHCPOFFER or DHCPACK?</p>
<p>It works after dhcp server restart, but then it starts again
after a whlie.</p>
<p>I tried to read isc-dhcp-server's source code but got bit
lost as it was hard to follow.</p>
<p>Thanks for any help.</p>
<p>Rado.</p>
<p><br>
</p>
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