how to configure standalone dns server for dhcp

Glenn Satchell Glenn.Satchell at uniq.com.au
Thu May 11 13:23:04 UTC 2006


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>Date: Wed, 10 May 2006 22:19:08 -0800
>From: kalyanasundaram S <s.kalyanasundaram at inbox.com>
>Subject: how to configure standalone dns server for dhcp
>To: dhcp-users at isc.org
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>Hi all,
> i am new to this place.
> I getting confuse with all ddns mailing list msgs.
> 
> I have a isolated setup with me.
> One server and one client.  
>
>  Server is configured with a static ip address whenever i want to connect to 
internet i plug in the network cable and use it. While running other services 
for test purpose i plugout the cable.. 
>ex like 
>-------
>IP:       (1.2.3.4)
>hostname : mydns
>
>  Client is configured to get ip address from dhcp.
>
>client hostname: abcd
>
>I want to run a DNS server and dhcp on the server and the client should get 
update its name on that dns..
>
>i simply followed the instruction in dhcpd.conf but still nothing had happed 
(host, dig says timed out or could not conect to server)
>

<snip>

>what should the resolv.conf file have?

resolv.conf on the client will be created by the dhcp client.

resolv.conf on the server should probably have:

domain example.com
nameserver 127.0.0.1

>is my configurations are correct.... how should i make it work? is my SOA 
records are correct?
>
>in all the times client is getting the ip address and i am able to ping to 
server and viceversa also.
>
>
>plz somebody help me to get it work.......
>
>thanks in advance.....
>
>regards,
>  -"kalyan"
>
>
If you use a fixed-address statement to assign a fixed address, then the dhcp 
server does not do dynamic dns updates for that address. The idea is, if the 
address is fixed then you can manually put itinto DNS and leave it there. To 
override that bahaviour use the update-static-leases statement.

% man dhcpd.conf
 ...
       update-static-leases flag;

       The update-static-leases flag, if enabled, causes the DHCP
       server to do DNS updates for clients even if those clients
       are being assigned their IP address using a  fixed-address
       statement  -  that  is, the client is being given a static
       assignment.   This can only  work  with  the  interim  DNS
       update  scheme.    It  is not recommended because the DHCP
       server has no way to tell that the update has  been  done,
       and therefore will not delete the record when it is not in
       use.   Also, the server must attempt the update each  time
       the  client  renews its lease, which could have a signifi-
       cant performance impact in environments that  place  heavy
       demands on the DHCP server.

Also, putting the host statement inside the subnet has no effect. host
statements are global in scope, so best to put them outside any other
scopes to avoid confusion later. The host statement will still pick up
the subnet setting sbecause an address in that subnet is being
assigned, not because iot is defined inside the subnet. eg, something
like this:

subnet 1.2.3.0 netmask 255.255.255.0 {
  range 1.2.3.20 1.2.3.35;
  default-lease-time 192000;
}
host test {
  hardware ethernet 00:02:47:1G:4D:E2;
  fixed-address 1.2.3.6;
}

Everything else in your dhcp/dns setup looks good.

regards,
-glenn



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