Change dhcp server IP address

[Simon Hobson]

Kone Bakenon - wrote:
>  > Kone Bakenon - wrote:
>>
>>>   > Can you post your config and a description of the network ?
>>
>>>Here you have my dhcpd.conf
>>>subnet 172.16.0.0 netmask 255.255.240.0
>>>{
>>>	range 172.16.1.1 172.16.15.254;
>>>	option subnet-mask 255.255.240.0;
>>>	option routers 172.16.0.1;
>>>	option broadcast-address 172.16.15.255;
>>>	option domaine-name "mydomain.bf";
>>>	option domaine-name-servers 206.82.130.195;
>>>	default lease-time 3600;
>>>	max-lease-time 7200;
>>>}
>>>
>>>subnet 172.16.16.0 netmask 255.255.240.0
>>>{
>>>	range 172.16.16.2 172.16.31.254;
>>>	option subnet-mask 255.255.240.0;
>>>	option routers 172.16.16.1;
>>>	option broadcast-address 172.16.31.255;
>>>	option domaine-name "mydomain.bf";
>>>	option domaine-name-servers 206.82.130.195;
>>>	default lease-time 3600;
>>>	max-lease-time 7200;
>>>}
>>
>>  That looks fairly normal, but you still haven't described the
>>  network, or explained what exactly isn't working.
>>
>>
>
>My network is subnetted in Vlan 3 and Vlan 4. The first time when a
>computer is on Vlan 3 or 4, it takes a good parameters but if the same
>computer is moved to another Vlan, all the parameters changes but only the
>IP address of dhcp server is the same.
>The IP address for dhcp server should be 172.16.0.1 on Vlan 3 and
>172.16.16.1 on Vlan 4.
>From Vlan 3 to Vlan 4, the IP address and the dhcp server address for the
>host computer should change but they don't.
>I think to be clear now.

No - it's still not clear as you have not adequately described your network.

I'm *guessing* that you don't have any routing between the VLANs, so 
a client with (say) 172.16.16.123 can't communicate with the DHCP 
server at 172.16.0.1.

If that is the case, then your network is broken and you should 
really be looking at fixing that.

I'm also *guessing* that the server is connected to both VLANs (is it 
the router ?). If so then you can probably work around the problem by 
setting the server-identifier option to give out the required server 
IP address in each subnet.

 From man dhcpd.conf :

           The server-identifier statement

             server-identifier hostname;

             The server-identifier statement can be used to define
             the  value that is sent in the DHCP Server Identifier
             option for a given scope.   The value specified  must
             be  an  IP  address  for the DHCP server, and must be
             reachable by  all  clients  served  by  a  particular
             scope.

             The  use  of  the  server-identifier statement is not
             recommended - the only reason to use it is to force a
             value  other  than  the  default  value to be sent on
             occasions where the default value would be incorrect.
             The  default value is the first IP address associated
             with the physical  network  interface  on  which  the
             request arrived.

             The  usual case where the server-identifier statement
             needs to be sent is when  a  physical  interface  has
             more  than  one IP address, and the one being sent by
             default isn't appropriate for  some  or  all  clients
             served  by  that  interface.   Another common case is
             when an alias is defined for the purpose of having  a
             consistent  IP address for the DHCP server, and it is
             desired that the clients use  this  IP  address  when
             contacting the server.

             Supplying  a  value  for  the  dhcp-server-identifier
             option is equivalent to using  the  server-identifier
             statement.