[Dnsmasq-discuss] Dnsmasq wont recieve DHCP request messaegs

Kiazada Dany-GVN438 GVN438 at motorolasolutions.com
Sun Feb 9 07:25:26 GMT 2014


Hi,

I'm using the program as a DHCP server for a Linux machine. The server needs to toggle between two different subnets, with different GW (on the same interface - 'br0'), and assign an IP for a windows PC.
So for example upon power up the DHCP will assign an IP to the PC (connected via Ethernet), with subnet 'A'.
After a while, the DHCP will need to assign a different IP, on a different subnet 'B'.
The way I implemented it is running dnsmasq on the Linux machine :

 -C /etc/dnsmasq.conf/sbin/dnsmasq -d --clear-on-rel

With The following  dnsmask.conf file (subnet 'A') :

dhcp-range=27.187.20.14,27.187.20.14,255.255.255.0,3600
interface=br0
dhcp-option=3,27.187.20.1
dhcp-option=6,27.187.20.1
dhcp-leasefile=/etc/dnsmasq.leases
dhcp-lease-max=253
log-dhcp

After I receive an indication to change the subnet, I kill the dnsmasq server, and run it again the same way only with the second subnet 'B'.
I noticed that the dnsmasq.leases is empty, and there are no connected clients after the second power up. The PC is sending DHCPINFORM messages (with no response) and
In order to have the PC ask for a new IP, I cut the power to the Ethernet Iface. This causing the PC to send DHCPREQUEST messages (with no DISCOVER messages before).
The dnsmasq is not responding to the REQUEST messages although it's a broadcast message, and I can see at tcpdump that they arrive to the Linux machine...

I can see in the app logs that the dnsmask is receiving the INFORM messages, but I cannot see the REQUEST messages (in the app logs).
The thing is the PC remembers the first IP it was assigned (subnet 'A'),  and although the DHCP server has a different IP range configuration, the PC is still showing the old IP.

So my goal is to have the PC assigned a new IP (without any PC involvement, meaning no ipconfig renew\release commands). from a different pool, different subnet and GW, after the dnsmasq is restarted.

Thank,
Dany

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