Sending IP range not in same range as Ethx

Simon Hobson dhcp1 at
Thu Aug 9 18:12:28 UTC 2012

Dod wrote:

>   I have a problem setting subnet that is not part of the IP range on
>   which the Eth of the machine running DHCP daemon is.
>   My need :
>   Send IP within to
>   mask
>   gateway
>   Problem  is that the Eth1 on wich the dhcp machine is running is not
>   in  10.19  range  so  when  I  start  it  it  say it cannot find any
>   interface with that subnet.

Correct, it will

>   Why  do  it  need  to be in same subnet ? is it for DHCP negociation
>   when  it  tries  to  echo  the  IP  it  will propose to see if it is
>   actually used ?

Because that's the way the server operates. You *MUST* have a subnet 
declaration that matches each subnet on all the interfaces teh server 
is listening on. If you aren't serving clients in a subnet then you 
can just leave it's declaration empty (specifically no range 

>   Second question, what is the parameter that permit to set
>   as gateway ?

Is this a locally attached subnet, or one that the other side of a router ?
Or put another way, are the server and clients on the same broadcast domain ?

If the clients are on the same network, then you have a shared 
network - look up shared-network in man dhcpd.conf.

If the clients are remote (ie not directly attached to the server), 
then all you need to do is configure a suitable DHCp Relay agent on 
the remote network and configure the right subnets in the DHCP server.

Simon Hobson

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