no Working leases on persistant database

Glenn Satchell Glenn.Satchell at
Wed Jan 16 13:48:27 UTC 2008

>Subject: Re: no Working leases on persistant database
>From: stephane lepain <s.lepain at>
>To: dhcp-users at
>Date: Wed, 16 Jan 2008 14:20:11 +0100
>Hi Simon, 
>Thank you for your resonse. From what you wrote, I have changed my
>network topology. Before the server had one NICS into my network and the
>other for the outside network (wan). Now I have my server with the two
>nics inside my network which allowed me to remove the dhcp client that
>was actually confusing me and the server :) 
>I have added a router/gateway to get to the wan. One if the NIC of my
>server is directly connected to it and the other NIC of the server is
>plugged into a switch. Anyhow, the server is now responding a lot better
>than before since the dhcp client is gone and the topology is quite

Ok, the configuration you had is actually quite common. The interface
facing the ISP can run a dhcp client to receive configuration info from
the ISP.

You seemed to almost have it working, the key piece is that the local
dhcp server has to be told to only listen on the interface with the
static IP address facing the internal network. In this configuration
the local dhcp server never sees a request from the dhcp client on the
other interface. I have used this type of setup a few times myself and
it can work quite well.

You didn't mention what operating system or distribution you were
using. The startup scripts for dhcpd are not part of the ISC
distribution, and each OS tends to do things slightly differently. It
may be that you adding the interface name to the wrong file, and this
was setting up the command line arguments in the wrong order perhaps.

Your configuration with the router should also work just fine.

>One last concern is that my ISP is using a dhcp as well. So I have got
>my own dhcp server within my network and my ISP using its own. Aren't
>they going to clash at some stage? My dhcp server is set to be

No. dhcp uses broadcasts to get from the client to the server. Unless
you badly misconfigure things, there should be no way for broadcast
network packets from your internal network to ever get to the ISP.

If you're on some sort of Cable or ADSL network, the DHCP at the ISP is
specifically set up to handle that, and would not assign arbitrary
addresses to your PCs on the local net.


>     1. Cheers 
>Le mardi 15 janvier 2008 à 19:12 +0000, Simon Hobson a écrit :
>> stephane lepain wrote:
>> >But the two NICS are configured in static. From my understanding it is
>> >good to prevent the DHCP client receiving DHCP service on the DHCP
>> >server.
>> Just DON'T RUN A DHCP CLIENT ! In the few Linux distributions I'm 
>> familiar with, if you statically configure the interface, it 
>> automatically stops using the dhcp client on it.
>> BTW - you are setting the interface configuration directly aren't 
>> you, ie not confusing "configure statically" with creating a host 
>> declaration for the DHCP server to give a specific address to a 
>> specific client ?
>> >Plus, how would that host declaration stop the dhcp server from
>> >working on one NIC.
>> It doesn't, it simply stops it responding to requests from that MAC address.

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