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Greetings

We see some unexpected behaviour of the DHCP server, assigning multiple IPs for the same MAC.
Diagnostics: DHCP leases
IP address    MAC address    Hostname    Start    End    
10.149.100.160     d0:bf:9c:dd:24:05          2015/02/12 15:29:31     2015/02/12 16:29:31     add a static mapping for this MAC address
10.149.100.165     d0:bf:9c:dd:24:05          2015/02/12 15:28:39     2015/02/12 16:28:39     add a static mapping for this MAC address
10.149.100.157     d0:bf:9c:dd:27:73          2015/02/12 15:29:19     2015/02/12 16:29:19     add a static mapping for this MAC address
10.149.100.170     d0:bf:9c:dd:27:73          2015/02/12 15:30:10     2015/02/12 16:30:10     add a static mapping for this MAC address
10.149.100.166     d0:bf:9c:dd:68:fe          2015/02/12 15:29:53     2015/02/12 16:29:53     add a static mapping for this MAC address
10.149.100.153     d0:bf:9c:dd:68:fe          2015/02/12 15:29:02     2015/02/12 16:29:02     add a static mapping for this MAC address
10.149.100.154     d0:bf:9c:dd:77:b8          2015/02/12 15:29:16     2015/02/12 16:29:16     add a static mapping for this MAC address
10.149.100.158     d0:bf:9c:dd:77:b8          2015/02/12 15:28:24     2015/02/12 16:28:24     add a static mapping for this MAC address
10.149.100.167     d0:bf:9c:dd:87:66          2015/02/12 15:28:26     2015/02/12 16:28:26     add a static mapping for this MAC address
10.149.100.162     d0:bf:9c:dd:87:66          2015/02/12 15:29:18     2015/02/12 16:29:18     add a static mapping for this MAC address
10.149.100.151     d0:bf:9c:dd:b8:c7          2015/02/12 15:29:31     2015/02/12 16:29:31     add a static mapping for this MAC address
10.149.100.168     d0:bf:9c:dd:b8:c7          2015/02/12 15:28:40     2015/02/12 16:28:40     add a static mapping for this MAC address
10.149.100.164     d0:bf:9c:dd:c8:91          2015/02/12 15:30:16     2015/02/12 16:30:16     add a static mapping for this MAC address
10.149.100.159     d0:bf:9c:dd:c8:91          2015/02/12 15:29:24     2015/02/12 16:29:24     add a static mapping for this MAC address
10.149.100.161     d0:bf:9c:dd:c8:9e          2015/02/12 15:29:33     2015/02/12 16:29:33     add a static mapping for this MAC address
10.149.100.155     d0:bf:9c:dd:c8:9e          2015/02/12 15:28:41     2015/02/12 16:28:41     add a static mapping for this MAC address
10.149.100.163     d0:bf:9c:dd:c8:e5          2015/02/12 15:28:45     2015/02/12 16:28:45     add a static mapping for this MAC address
10.149.100.152     d0:bf:9c:dd:c8:e5          2015/02/12 15:29:37     2015/02/12 16:29:37     add a static mapping for this MAC address
10.149.100.190     d0:bf:9c:dd:e8:0c          2015/02/12 16:28:20     2015/02/12 17:28:20     add a static mapping for this MAC address


As this makes our PC Deployment go nuts, I wonder if there's anything we can do against it.

First obvous observation is the suspiciously short lease time of <1 Second...

Thanks and best regards,
HP.

Actually, the lease time is an hour...  But why it is asking twice in one hour is odd...  Look in the logs and see if you are getting offers with no ack.

Thanks Lee!

Of course you are right. (Whoever DOES read has an advantage  )

Going on sniffing/tcpdumping tour. and will report...

Actually, bumping the system logs in m0n0wall to 300 or so and looking in there will tell you a lot about DHCP errors.