ddns correct settings for dhcp when accepting client host names

Steve Brown radclif444 at gmail.com
Sun Dec 1 09:55:08 UTC 2013

Hi I just have a quick question,
I have recently set up dynamic dns with dhcp 4 and bind 9.
Everything is working as it should except for a handful of hosts on the
network which don't resolve. Upon investigating I found they had been
dynamically added into the bind zone file but they had their host name
appended with the domain name.

for example server1 is fine but server2 wont resolve:

    $TTL 1800 ; 30 minutes
    server1                 A
     TXT "00ecbb5990a60bb0b138272611cae0f56d"
    server2.reh.favsys.net A
    TXT "00ecbb5990a60bb0b138272611cae0f56d"

I checked out server2 to see what was different
I found that in the /etc/sysconfig/netowrk-scripts/ifcfg-eth0 file the
DHCP_HOSTNAME option was set with a fqdn:
where as server1 had just the host name:

Right so I guess I just have to find all the servers with this problem and
change the interface file to just contain the host name.

That's fine and could be done but is this the right way to configure the
interface file?
should the the DHCP_HOSTNAME option be an unqualified name.

Or is there a setting I can turn on in the DHCP server's configuration file
to stop this kind of behaviour from happening. If there was a way to
configure dhcp to disregard the domain part if a client sent in its host
name fully qualified I would much rather take this approach.

my current dhcpd.conf options are:

    include "/etc/rndc.key";
    ddns-update-style interim;
    ddns-domainname         "my.domain.net.";
    ddns-rev-domainname     "in-addr.arpa.";
    ddns-updates            on;
    ignore client-updates;
    option domain-search "my.domain.net";
    default-lease-time 1800;
    max-lease-time 7200;
    log-facility local7;

I also tried configuring the dhcp server with allow client-updates to see
if it would make a difference. However this just led to a dynamic update
entry in the zone file like this:

    $ORIGIN my.domain.net.
    $TTL 1800 ; 30 minutes
    server1                 A
    TXT "009ddasdr32rfdsfksdfpdsadsad3343fcdsd"
    $ORIGIN my.domain.net.my.domain.net.
    server2          A
    TXT "dasdasdsadasdsddvc0b1382726dsdadasdsd"

A new origin was created with the domain name repeated and the host name
was still not resolvable.

I would really appreciate any pointers on the correct way to configure
sending host names from clients  when using dhcp and bind for ddns thanks.
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