[Dnsmasq-discuss] Slow response to DHCPDISCOVER
daryl at isletech.net
Tue Apr 24 15:51:31 BST 2012
Actually, the "10 dollar domestic router" fix points to the probable
solution. You likely have spanning tree turned on on your usual switch,
which will block all traffic on that port for the first 50 seconds after
a link state change. Either switch to rapid spanning tree, or look into
your switch's version of "portfast"..
On 12-04-23 11:21 PM, Adrian May wrote:
> Hi Simon,
> In the meantime I installed ClearOS, which uses dnsmasq. Now the PCs
> get served fast but my embedded boards are still not getting IPs. If I
> plug these embedded boards into my 10 dollar domestic router, they get
> an IP instantly. I already tried setting bootp-dynamic and
> dhcp-broadcast in the config. If I grep everything under /var/log for
> dnsmasq, there's no evidence that requests were even received from
> these boards. So I still suspect the networking layer.
> As for the boards themselves, I'm not entirely sure what they do.
> They've got some kind of embedded linux. One boots into yamon where I
> can only say "net init", the other into something of its own invention
> where I start udhcpc.
> I tried no-ping but it had no effect. I can't get my brain around your
> tag system. I've just been writing things like bootp-dynamic with no
> tags right in the main config file, or in the case of ClearOS, in the
> dhcp config file which is referenced from the main config file. Could
> it be that these settings have no effect unless I attach some tags, or
> put them inside a subnet declaration?
> On 04/23/2012 08:01 PM, Simon Kelley wrote:
>> 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?
>>> Dnsmasq-discuss mailing list
>>> Dnsmasq-discuss at lists.thekelleys.org.uk
>> Dnsmasq-discuss mailing list
>> Dnsmasq-discuss at lists.thekelleys.org.uk
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