DHCP Duplicate IPs

Nathan McDavit-Van Fleet nmcdavit at alcor.concordia.ca
Fri Jan 14 13:58:31 UTC 2011


I deleted both dhcpd.leases files on my servers. I hope that whatever
persistent leases are deleted. Does anyone have a suggestion as to why this
might have happened?

Nathan Van Fleet


> -----Original Message-----
> From: dhcp-users-bounces+nmcdavit=alcor.concordia.ca at lists.isc.org
> [mailto:dhcp-users-bounces+nmcdavit=alcor.concordia.ca at lists.isc.org]
> On Behalf Of Nathan McDavit-Van Fleet
> Sent: Wednesday, January 12, 2011 9:13 AM
> To: 'Users of ISC DHCP'
> Subject: DHCP Duplicate IPs
> 
> We are having some issues with duplicates in the system where clients
> might
> have two IPs in the dhcp leases, even on the same subnet. We only allow
> one-ip-per-client but there appears to be duplicates since we started
> getting this error:
> 
> "dhcpd: uid lease 192.168.1.150 for client xx:xx:xx:xx:xx:xx is
> duplicate on
> 192.168.1/24"
> 
> I think it might have to do with the servers being out of
> synchronization.
> So the client gets an IP from the low range of the subnet from server A
> and
> then one IP from the high range from server B. It's odd because I get
> very
> persistent errors about sync refusal that never resolve (dhcp-failover
> rejected: incoming update is less critical than outgoing update).
> 
> I did some online research and came across this page:
> "http://www.culmination.org/2008/10/28/isc-dhcpd-duplicate-uid-lease/".
> I
> noticed that there is a suggestion in the comments to include "deny
> duplicates;" in the dhcpd.conf. It appears to work as expected, but I'm
> not
> sure if this is just covering up the real problem and not actually
> correcting it. We're still getting the same error, but it does not
> appear to
> repeat for the same user. So I hope that it's keeping the dhcpd.leases
> file
> clean of conflicts?
> 
> 
> Detailed log for one user
> Jan 12 07:22:30 shining dhcpd: DHCPREQUEST for 192.168.2.11 from
> 00:bb:aa:cc:00:bb:aa:cc via 10.106.155.3: wrong network.
> Jan 12 07:22:30 shining dhcpd: DHCPNAK on 192.168.2.11 to
> 00:bb:aa:cc:00:bb:aa:cc via 10.106.155.3
> Jan 12 07:22:30 shining dhcpd: DHCPDISCOVER from
> 00:bb:aa:cc:00:bb:aa:cc via
> 10.106.155.3: load balance to peer iits-dhcp-failover
> Jan 12 07:48:47 shining dhcpd: DHCPDISCOVER from
> 00:bb:aa:cc:00:bb:aa:cc via
> 10.106.228.1
> Jan 12 07:48:48 shining dhcpd: DHCPOFFER on 10.106.229.128 to
> 00:bb:aa:cc:00:bb:aa:cc (DTiPod) via 10.106.228.1
> Jan 12 07:48:49 shining dhcpd: DHCPREQUEST for 10.106.229.128
> (10.106.101.3)
> from 00:bb:aa:cc:00:bb:aa:cc (DTiPod) via 10.106.228.1
> Jan 12 07:48:49 shining dhcpd: DHCPACK on 10.106.229.128 to
> 00:bb:aa:cc:00:bb:aa:cc (DTiPod) via 10.106.228.1
> Jan 12 08:02:31 shining dhcpd: DHCPREQUEST for 10.106.229.128 from
> 00:bb:aa:cc:00:bb:aa:cc (DTiPod) via 10.106.228.1
> Jan 12 08:02:31 shining dhcpd: DHCPACK on 10.106.229.128 to
> 00:bb:aa:cc:00:bb:aa:cc (DTiPod) via 10.106.228.1
> Jan 12 08:05:23 shining dhcpd: DHCPREQUEST for 10.106.229.128 from
> 00:bb:aa:cc:00:bb:aa:cc (DTiPod) via 10.106.155.3: wrong network.
> Jan 12 08:05:23 shining dhcpd: DHCPNAK on 10.106.229.128 to
> 00:bb:aa:cc:00:bb:aa:cc via 10.106.155.3
> Jan 12 08:05:23 shining dhcpd: DHCPDISCOVER from
> 00:bb:aa:cc:00:bb:aa:cc via
> 10.106.155.3: load balance to peer iits-dhcp-failover
> Jan 12 08:26:31 shining dhcpd: DHCPDISCOVER from
> 00:bb:aa:cc:00:bb:aa:cc via
> 10.106.155.3
> Jan 12 08:26:32 shining dhcpd: DHCPOFFER on 10.106.155.203 to
> 00:bb:aa:cc:00:bb:aa:cc (DTiPod) via 10.106.155.3
> Jan 12 08:26:33 shining dhcpd: DHCPREQUEST for 10.106.155.203
> (10.106.101.3)
> from 00:bb:aa:cc:00:bb:aa:cc (DTiPod) via 10.106.155.3
> Jan 12 08:26:33 shining dhcpd: DHCPACK on 10.106.155.203 to
> 00:bb:aa:cc:00:bb:aa:cc (DTiPod) via 10.106.155.3
> Jan 12 08:29:29 shining dhcpd: DHCPREQUEST for 10.106.155.203 from
> 00:bb:aa:cc:00:bb:aa:cc (DTiPod) via 10.106.228.1: wrong network.
> Jan 12 08:29:29 shining dhcpd: DHCPNAK on 10.106.155.203 to
> 00:bb:aa:cc:00:bb:aa:cc via 10.106.228.1
> Jan 12 08:29:29 shining dhcpd: DHCPDISCOVER from
> 00:bb:aa:cc:00:bb:aa:cc via
> 10.106.228.1: load balance to peer iits-dhcp-failover
> Jan 12 08:29:32 shining dhcpd: uid lease 10.106.229.128 for client
> 00:bb:aa:cc:00:bb:aa:cc is duplicate on 10.106.228.0/23
> Jan 12 08:29:32 shining dhcpd: DHCPREQUEST for 10.106.229.115
> (10.106.140.240) from 00:bb:aa:cc:00:bb:aa:cc via 10.106.228.1: lease
> owned
> by peer
> Jan 12 09:00:51 shining dhcpd: DHCPDISCOVER from
> 00:bb:aa:cc:00:bb:aa:cc via
> 10.106.228.1: load balance to peer iits-dhcp-failover
> Jan 12 09:00:53 shining dhcpd: uid lease 10.106.229.128 for client
> 00:bb:aa:cc:00:bb:aa:cc is duplicate on 10.106.228.0/23
> Jan 12 09:00:53 shining dhcpd: DHCPREQUEST for 10.106.229.149
> (10.106.140.240) from 00:bb:aa:cc:00:bb:aa:cc via 10.106.228.1: lease
> owned
> by peer
> Regards,
> 
> Nathan Van Fleet
> 
> 
> 
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