[Dnsmasq-discuss] dhcpoffer's not being accepted?

Simon Kelley simon at thekelleys.org.uk
Fri Oct 14 21:31:24 BST 2005

Aaron J Weber wrote:
> I have a new RH ES 4 box I'm trying to bring online.
> It's setup for dhcp and I see my dnsmasq receiving the requests in the 
> messages (syslog) on that host.  It also says it's replying with 
> DHCPOFFER's of valid IP addresses.  But for some reason the RH box 
> refuses to bring up eth0 -- it's apparently not receiving the DHCP 
> replies or it doesn't like the format of them or something???
> I don't see this occur with my windoze clients.
> Can anyone help me troubleshoot?  I can find my way around Linux pretty 
> well, so if you have some places to look and/or debug settings for 
> client or server side of the DHCP that would help.

Which DHCP client are you using on RedHat? Have you tried a different 
one? Are there any firewall/iptables rules in place on the RedHat Box?

If Windoze, works on the same network, and you're seeing dnsmasq log 
DHCPOFFERS, it's highly unlikely to be a dnsmasq configuration problem. 
Every once in a while, someone comes across a client which works with 
the ISC DHCP server, but doesn't work with dnsmasq. (almost always, said 
client turns out to be buggy, and someone hacked on it just long enough 
to work with ISC server, but not long enough to get it right.) But 
that's normally some obscure embeded client in a printer, or suchlike, 
all of the common Linux DHCP clients are known to work fine.

> Maybe there's one or more of the dnsmasq settings I should tweak? 


> I 
> have the dhcp-authoritative set to TRUE (as it applies), but could it be 
> causing an issue?

I can't think of a way that it could.

Try these.

1) Another DHCP client.
2) Remove all firewall rules.
3) Use ethereal/tcpdump to check that the OFFER packets are getting out 
onto the network.

> Please, please help?
> -AJ


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