[NTLUG:Discuss] dhcp question

[Rick Renshaw]

--- Ed Leach <ntlug at levelofdetail.com> wrote:
> 
> I have 2 CentOS machines on the same network. I have a dhcp server set
> up. I'm restarting networking on a client machine in the same network.
> It finds the dhcp server and restarts networking, but it is not being
> updated with a new IP address.
> 
> On the server I'm getting this error in /var/log/messages:
> 
> ---
> localhost dhcpd: DHCPREQUEST for 192.168.0.103 from 00:11:31:f1:3b:bc
> via eth0: unknown lease 192.168.0.103.
> ---
> 
> 192.168.0.103 is the IP address of the client that I believe the client
> is getting from the router. Why wouldn't the client get it's IP address
> from the dhcp server?
> 
> Below is my config file, which I have simplified as much as possible but
> is still not working.
> 
> Also - I'm studying to take the RHCE exam some time and am looking for
> some help if there is someone in the North Dallas or Plano area who
> could provide advice and/or some kind of mentoring (like testing me).
> I'm going through Jang's prep book and every once in a while get tripped
> up by something like the above problem.
> 
> Thanks,
> 
> Ed
> 
> ------------------------------
> 
> ddns-update-style interim;
> ignore client-updates;
> 
> subnet 192.168.0.0 netmask 255.255.255.0 {
> 
> option routers 192.168.0.1;
> option subnet-mask 255.255.255.0;
> 
> option time-offset -18000; # Eastern Standard Time
> 
> range dynamic-bootp 192.168.0.128 192.168.0.254;
> default-lease-time 21600;
> max-lease-time 43200;
> }

DHCP is a broadcast protocol, and any valid DHCP server on the network can answer.  The client
then usually takes the first offer and uses that address.  The router is probably answering first,
so the client is using that address.

If you want to use the DHCP server on your CentOS box, you should turn off DHCP on the router and
assign a static address to the DHCP server.


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