isc-dhcpd server, HOSTNAME

Pieter Donche Pieter.Donche at
Sun May 10 06:15:17 UTC 2009

On Sat, 9 May 2009, Mel Flynn wrote:

> On Saturday 09 May 2009 15:09:45 Pieter Donche wrote:
>> case DHCP server             DHCP client       HOSTNAME env. var.
>>   1   isc-dhcp30-server       FreeBSD7-i386     not set
>>        on FreeBSD-amd64
>>   2   isc-dhcp30-server       SuSE Linux 10.3   set
>>        on FreeBSD-amd64
>>   3   some DHCP server        FreeBSD7-i386     set
>>        on unkown serverOS
>>   4   some DHCP server        SuSE Linux 10.3   set
>>         on unkown serverOS
> Judging from this, you have a hostname set in /etc/rc.conf on freebsd 7 client
> and/or dhcpd isn't configured to send one as it receives one from the client
> and perhaps you have dynamic DNS configured?

There is no hostname= declaration in /etc/rc.conf in that FreeBSD7 dhcp client.

My dhcpd.conf contains mostly statically defined addresses (over a 100)
host somehostname { hardware ethernet aa:bb:cc:dd:ee:ff; fixed-address AAA.BBB.CCC.DDD; }
and one set of 6 dynamically assigned addresses.

We want regular users to always get the same IP address based on the MAC
address of their system, the pool of 6 is for visitors for one or a few
days that we do allow not to register their MAC address.

The freebsd7 client is one of the 100+ statically assigned ones, but
I might have done a try for the dynamic assignment with this PC (by taking
it temporarily out of /usr/local/etc/dhcpd.conf, restart dhcpd, try, 
then put it back in, restart dhcpd.

In fact in /var/db/dhcpd/dhcpd.conf I see I do have an entry
   starts 4 2009/05/07 12:49:13;
   ends 4 2009/05/07 13:19:16;
   tstp 4 2009/05/07 13:19:16;
   binding state free;
   hardware ethernet;
   uid "\001\000\013\333S>\025";
AAA.BBB.CCC.DDD being one of the pool of 6 and the ethernet adddress that
of the freebsd client.

I see that's "free'd" already (max lease time is 12 hours) and I tried back 
with that entry again as a statically defined one. Or does this 
entry still have an impact ???

The man of dhcpd.leases says "In  order to prevent the lease database 
from growing without bound, the file is rewritten from time to time."
Can one do such a "rewrite" oneself, how ? would that help?

On the other hand the AAA.BBB.CCC.DDD IP address does have a hostname
specified in the DNS server (somewhere in our campus) (and that DNS
server can be queried from the freebsd client via nslookup or host 
command and it returns the correct hostname). So even in dynamic assignment, 
shouldn't HOSTNAME been set with that hostname from DNS?

> If that's not the case, then you should add some debugging to /sbin/dhclient-
> script in the check_hostname function.
> -- 
> Mel

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