[Dnsmasq-discuss] DHCP request not getting to dnsmasq

Guennadi Liakhovetski g.liakhovetski at gmx.de
Sun Dec 23 21:04:42 GMT 2007


On Sun, 23 Dec 2007, Robin Atwood wrote:

> This is probably something stupid but I am new at dnsmasq. I have the DNS 
> function working well but wanted to run DHCP as well, for the laptops and 
> PDAs in the house. Dnsmasq is running on a server which is plugged directly 
> into an ADSL WiFi router, which is the gateway. When I activate the interface 
> on a laptop, it connects over the WLAN to the router but when dhcpcd runs, it 
> just times-out. The router is not running DHCP. I thought the DHCP client 
> searched the LAN for a server but nothing appears in the dnsmasq logging. The 
> firewall rules look Ok, so what have I overlooked?

I also have a DSL router with WLAN and ethernet interfaces, and it is 
supposed to be used with _either_ one or another, and I never checked and 
don't know whether a connection is possible between clients connected over 
WLAN and ethernet. If you configure the interface on your laptop manually, 
can you ping your dnsmasq server?

If this works, try start on your dnsmasq server as root, before connecting 
your laptop

tcpdump -i eth0 port 67

then, as your laptop comes up and tries to get a dhcp lease, you should 
see tcpdump output something like this

21:59:50.381445 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, 
Request from 00:50:bf:a4:59:71 (oui Unknown), length 300

I would guess you don't get this far. Then try to find out why this 
doesn't work. It might be, for example, that the router doesn't pass 
broadcast requests from WLAN to ethernet (would be evil, but who knows). 
Let us know the results.

Thanks
Guennadi
---
Guennadi Liakhovetski



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