Curious lease to/from Apple DHCP Client

Tue Aug 1 15:04:38 UTC 2006

Hi everybody.
We are running two ISC Dhcpd (version 3.0.4) configured in a failover 
mode. The max-lease-time is of 3600 sec and the default-lease-time of 
900 sec.

We noticed a curious comportment from several Apple clients, where they 
always do a DHCP DISCOVER at the end of the lease time. Each time 
requesting a lease of 90 days. The OFFER/REQUEST/ACK sequence that 
follows this DISCOVER is correct, the server offers a lease time of 
60s... but  90 sec later (not 30s or 60s !!), the client does a DISCOVER 
again, requesting a lease of 90 days.

The ISC server OFFER another address with a lease of 60 sec, and so on...

Here is an example (a scripted output of a tcpdump) : LT is the Lease 
Time, each line represents an exchange between the client and the server :

Host 00:11:24:e3:54:9e did a DISCOVER at 16:30:32.000920 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:30:33.006151 with IP 
Address vis193b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:30:33.008401 with a LT of 0 
and received a ACK with a LT of 60 at 16:30:40.627665 with IP Address 
vis193b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:32:03.000778 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:32:04.007340 with IP 
Address vis174b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:32:04.010728 with a LT of 0 
and received a ACK with a LT of 60 at 16:32:05.839760 with IP Address 
vis174b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:33:34.001017 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:33:35.008029 with IP 
Address vis177b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:33:35.010371 with a LT of 0 
and received a ACK with a LT of 60 at 16:33:40.330396 with IP Address 
vis177b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:35:05.000179 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:35:06.007092 with IP 
Address vis124b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:35:06.008747 with a LT of 0 
and received a ACK with a LT of 60 at 16:35:07.149920 with IP Address 
vis124b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:36:36.000091 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:36:36.045972 with IP 
Address vis201b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:36:37.010422 with a LT of 0 
and received a ACK with a LT of 60 at 16:36:51.195181 with IP Address 
vis201b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:38:07.000977 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:38:08.011843 with IP 
Address vis049b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:38:08.013300 with a LT of 0 
and received a ACK with a LT of 60 at 16:38:12.271460 with IP Address 
vis049b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:39:38.001363 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:39:39.006160 with IP 
Address vis166b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:39:39.008478 with a LT of 0 
and received a ACK with a LT of 60 at 16:39:45.668114 with IP Address 
vis166b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:41:09.000244 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:41:09.154725 with IP 
Address vis176b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:41:10.008638 with a LT of 0 
and received a ACK with a LT of 60 at 16:41:10.013470 with IP Address 
vis176b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:42:40.000701 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:42:41.006162 with IP 
Address vis103b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:42:41.009321 with a LT of 0 
and received a ACK with a LT of 60 at 16:42:49.791866 with IP Address 
vis103b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:44:11.000930 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:44:12.006226 with IP 
Address vis028b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:44:12.009056 with a LT of 0 
and received a ACK with a LT of 60 at 16:44:20.535706 with IP Address 
vis028b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:45:42.001526 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:45:43.007352 with IP 
Address vis066b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:45:43.010073 with a LT of 0 
and received a ACK with a LT of 60 at 16:45:46.097156 with IP Address 
vis066b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:47:13.002257 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:47:13.834445 with IP 
Address vis205b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:47:14.012566 with a LT of 0 
and received a ACK with a LT of 60 at 16:47:15.370664 with IP Address 
vis205b.inria.fr
Host 00:11:24:e3:54:9e did a DISCOVER at 16:48:44.000115 with a LT of 
7776000 and received a OFFER with a LT of 60 at 16:48:45.006587 with IP 
Address vis227b.inria.fr
Host 00:11:24:e3:54:9e did a REQUEST at 16:48:45.009026 with a LT of 0 
and received a ACK with a LT of 60 at 16:48:46.447237 with IP Address 
vis227b.inria.fr

In the mean time another host (an other Mac) do this :

Host 00:0d:93:ec:91:2a did a REQUEST at 16:30:50.618461 with a LT of 
7776000 and received a ACK with a LT of 528 at 16:30:52.226134 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:38:53.689811 with a LT of 
7776000 and received a ACK with a LT of 3441 at 16:38:54.297431 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:42:03.975267 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:42:05.434904 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a DISCOVER at 16:43:53.425582 with a LT of 
7776000 and received a OFFER with a LT of 3600 at 16:43:57.653142 with 
IP Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:45:47.005356 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:45:47.016028 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:45:48.854430 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:45:50.234421 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:46:19.980490 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:46:23.355683 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:49:07.994421 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:49:09.576512 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:50:16.944071 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:50:20.989054 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:50:56.369235 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:51:05.314977 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:53:26.007620 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:53:38.123179 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:54:57.018200 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:54:58.827988 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:54:58.830238 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:55:03.496919 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:56:49.044889 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:56:50.230835 with IP 
Address vis145b.inria.fr
Host 00:0d:93:ec:91:2a did a REQUEST at 16:56:50.232835 with a LT of 
7776000 and received a ACK with a LT of 3600 at 16:56:58.183621 with IP 
Address vis145b.inria.fr

Does anybody have an idea of what's going on in the first case ?

Regards,

-- 
Didier Benza                            Didier.Benza at sophia.inria.fr
Tel : +33 492 38 7167 /  Fax : +33 492 38 7602 
INRIA 2004, Route des Lucioles, BP  93, 06902 Sophia Antipolis Cedex
AC INRIA : http://igc.national.inria.fr/Doc/General/CertAC.html#certif