SV: DISCOVER bursts

[Glenn Satchell]

There was a bug fix recently wrt to lease limit. When a lease is
offered it has a 2 minute lease duration. If the client then comes back
and requests it the lease offered has the normal lease duration
(whatever you configured, or the client asked for). Until the lease is
requested it's a sort-of temporary lease and not part of the lease
limit yet.

Does the dhcp client eventually accept one of the offers and send a
request for it? If so, then the other temporary leases will expire in
two minutes and go back to being available for other clients.

Yes, it sounds like a client that's not well written, but the client
should handle these cases and try to do something sensible.

Not sure how many clients you have, but I suspect a Sun V210 could
handle 10-50,000 clients easily depending on the lease time.

regards,
-glenn
--
Glenn Satchell     mailto:glenn.satchell at uniq.com.au | Some days we are
Uniq Advances Pty Ltd         http://www.uniq.com.au | the flies;  some
PO Box 70 Paddington NSW Australia 2021              | days we  are the
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>From: "Lars Jacobsen" <lars-jacobsen at newmail.dk>
>To: <dhcp-users at isc.org>
>Subject: SV: DISCOVER bursts
>Date: Sat, 6 Jan 2007 20:23:35 +0100
>
>Well I read the question as regardless of the CPE "misbehaver" (asking for
>an IP address 4 times) the server should NEVER offer more than max two
>addresses to a client in this particular config. But it does, why ?
>
>I expect Staffan has:
>spawn with option agent.circuit-id;
>lease limit 2;
>somewhere in his config.
>
>Maybe as suggested an race/timing issue inside the server, keeping track on
>offered not yet acknowledged leases, compared to some of the rules for this
>specific client.
>
>
>/Lars
>
>
>
>> -----Oprindelig meddelelse-----
>> Fra: dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org] På vegne
>> af Milton W. Schober, Jr.
>> Sendt: 5. januar 2007 15:56
>> Til: dhcp-users at isc.org
>> Emne: Re: DISCOVER bursts
>> 
>> What is the CPE?  We have seen something similar with Thomson IPTV set top
>> boxes, but the problem is in the STB, not the server.
>> 
>> Milton Schober
>> ----- Original Message -----
>> From: <Staffan.Ungsgard at teliasonera.com>
>> To: <dhcp-users at isc.org>
>> Sent: Friday, January 05, 2007 3:55 AM
>> Subject: DISCOVER bursts
>> 
>> 
>> > Hi
>> > We have problem with a special customers CPE, where the CPE send four
>> > rapid DHCPDISCOVERS with just 20 milliseconds apart.
>> > When the DHCP server gets the DISCOVERS it issues different addresses on
>> > each discover. I have snoop logs of the traffic, and the DISCOVERS are
>> > indeed exactly the same in each DHCPDISCOVER. It seems that the when the
>> > server handles the second DISCOVER, it doesn't "remeber" that is has
>> > already offered a fresh ip address from an identical DHCPDISCOVER 20 ms
>> > earlier.
>> > To furthermore illustrate this, we have a lease limit of two, so
>> > technically it shouldn't offer more than two addresses to the same line
>> > identifier even if the "Client Identifier" differed, but it isses three
>> > different addresses and only barfs at the fourth DHCPDISCOVER saying "no
>> > billing".
>> >
>> > Is there a race problem in the dhcp server ?
>> >
>> > The hardware is a Sun V210 running Solaris 8. No supermachine, but
>> they're
>> > still selling them.
>> >
>> > Best Regards
>> >
>> > -- Staffan Ungsgard