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-   -   DHCP excluding IP addresses (

AndyJ 02-28-2003 01:30 PM

DHCP excluding IP addresses
It's a bit strange this one. I have a home network with an ADSL router (Solwise SAR110) acting as a DHCP server. There are upto 4 pcs on the network: 1 win XP box, 1 OSX powerbook, 1 win 2k laptop (occasionally), and 1 Suse 8.1 Linux box. The machines are regularly turned off. All the boxes except the Linux box work fine, this is the symptom I am having with Linux:

When it starts up it requests an IP address from the DHCP server and receives one. When I restart it, it requests an IP address from the DHCP server and receives one IF ONE IS AVAILABLE. What is happening, is that the old IP address is going into the DHCP server's excluded address list (when I turn off the Linux box I think), so the Linux box is receiving a different address each time. It never receives an address previously used by one of the other machines (which always receive the same address). Eventually the DHCP server runs out of addresses and the Linux box is unable to connect to the network. I have to manually remove the excluded addresses from the server and reboot the server and the Linux box.

Can anyone tell me why the server might be automatically excluding the IP address and how I might resolve it?

andresurzagasti 02-28-2003 07:24 PM

Hi. Can you post or send to me your dhcpd.conf ?

AndyJ 03-02-2003 03:47 PM

Sorry it's taken so long but I've been away over the weekend. I've attached a copy of the file. I've also noticed that during bootup when it is trying to obtain an address from the DHCP server that it times out and backgrounds the operation - this still succeeds if there is an address available

I don't have a dhcpd.conf file but then if the Linux box is running as a dhcp client would it need one? Doesn't it use dhcpcd? I don't know what, if any, configuration file that uses otherwise I would post it.

If you could point me as to whether I need to install anything or any possible solutions I would be grateful.


andresurzagasti 03-03-2003 09:33 AM

Sorry, I thinked that the dhcp server are Linux box (... read very fast...)

I cannot help to you with the ADSL router, because I cannot these configuration. Sow, if you converts the linux box in a DHCPD server, itīs not problem for me the configuration.


AndyJ 03-03-2003 12:31 PM

Thanks anyway.

cojo 03-03-2003 01:16 PM

Andy, what kind of error are you getting? Is your Provider use pppoe? If so, I assumed it's setup on your Linux box. When your linux box finished booting up. Could you manually obtain an IP from the router?

AndyJ 03-03-2003 01:33 PM

I'm not getting an error as such. During bootup I see that it backgrounds the DHCP request after waiting a little while, but it always does that. It works whilst there are spare ip addresses in the routers address range, but on each boot, the last address is added to the excluded list by the router itself and a new one issued. Eventually the router runs out of addresses and then if I ping a machine, for example, it tells me that the network is unavailable.

It uses PPoA VC-Mux.

cojo 03-03-2003 02:12 PM

I'm don't know anything about your router. But, it sound like a setting in your router is not releasing the IP properly with linux. Have you look into your router setting yet? As far as I know, dhcp client doesn't do much beside optain an IP from you dhcp server(ADSL router). Usually, dhcp client will use the same IP everytime it bootup anyway. You could always assign a static to your linux box. I couldn't find anything about your router on the web at all. Sorry, I can't be anymore helpful.

AndyJ 03-03-2003 03:09 PM

No problems - thanks for your time.

There aren't many settings to get wrong on the router and it works for the other two pcs connected. AFAIK, the client requests an address using its MAC address - this is then stored in the address table along with the assigned address for as long as the lease lasts (which isn't very long in this case!!). The server uses this MAC address to find a currently active lease to reassign.

I can only think it must be something with the config on the Linux box. IP Spoofing? Firewall? I've noticed in the boot log that IP forwarding is disabled. The dhcpcd command executed is
/sbin/dhcpcd -H -D -N -Y -t 999999 -h linux eth0

I've asked on the Solwise forum to see what circumstances cause the router to auto add entries to the excluded list to see if that gives me any clues.

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