Multiple DHCP Server configuration in a single LAN

Simon Hobson dhcp1 at
Thu Mar 27 12:37:19 UTC 2008

Rajiv Rajaian wrote:

>I have configured DHCP server in my machine connected to LAN which 
>is having Scientific Linux OS
>dhcp-3.0.1-12_EL.i386 is the version I've configured
>Also there is one DHCP server configured with windows OS in my LAN
>Now all the dhcp  client requests are acquiring Ip address from the 
>Windows DHCP Server.
>Is there any possiblity to have the multiple DHCP Servers in a single LAN ??
>Whether I ve to do any other configuration in client machine so that 
>i ve to request ip address explicitly to the Linux DHCP server?

You can NOT do this without configuration on BOTH servers to support it<period>

If you do not configure BOTH servers to suit your needs then you WILL 
have problems of clients getting leases from the wrong server.

Typically, what you will need to do is decide on how to identify your 
clients (mac address list, client-ids, hardware vendor, dhcp option, 
something else). Then you must configure one server to ignore one set 
of clients, and the other server to only service the same set of 
clients. The addresses the two servers hand out must be 
non-overlapping, and if they are serving up different subnets, then 
BOTH servers must be correctly configured to handle the resulting 

How you might do things for a small number of clients on teh second server is :
- Define the set of clients by MAC address, and add either class or 
host statements for them.
- Define a config that only services those clients, eg :
-- Use host statements and "deny unknown clients"
-- Use a class (and subclass) and add 'allow "classname"' to the pool 
- Configure the main server to ignore those clients.

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