[Dnsmasq-discuss] Slow response to DHCPDISCOVER

Simon Kelley simon at thekelleys.org.uk
Mon Apr 23 13:01:43 BST 2012

On 23/04/12 12:02, Adrian May wrote:
> Hi all,
> I get the same result with dnsmasq, dhcp3-server and isc, namely, that
> the client has to send several DHCPDISCOVER packets before the server
> finally responds after about 30 seconds. This is breaking a couple of
> embedded platforms because they aren't that patient, and I have no way
> of configuring that.
> Why don't DHCP servers just respond to the first DHCPDISCOVER?
> Especially when I made them authoritative?#

Servers allocate an address and then ping it for a few seconds just to 
be sure it's not in use. That's the main delay. In dnsmasq --no-ping 
will stop this behaviour. Also the  client is entitled to wait around 
collecting answers from more than one server before deciding which one 
to use; they rarely do this and it doesn't sound like yours are.
> I think I might have seen in the logs that the dhcp processes aren't
> even getting the earlier packets, even though the machine is. It's as if
> they get discarded by the networking layer. This is a ubuntu server
> 10.04 machine.

Firewall rules can affect things, but the result is rarely intermittent. 
Is your network heavily loaded and dropping packets?



> Any ideas?
> Adrian.
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