- ERPOE ver 1.8.0
- We get these in the message file
- Happens EVERY 12 hours
- ALL are from Ubiquiti devices
- ALL devices have STATIC IP
- ALL LANS are set: Authoritive enable
- ALL below devices on same LAN
- ALL devices have no WAN access (no port forwards, no open ports)
- ALL devices have blocked access from other LANS and vLANS (no pings possible)
- ALL devices have same settings (ex: Telnet disabled, fw 5.6.5, etc)
- ALL devices are CLEAN, no scripts, no virus
- AirControl2 not running on LAN, but used only once in a while
I have read all other posts pertaining to this issue
This clutters message file
\var\log\messages HAPPENS EVERY 12 hours !!!!!!!!!!! May 19 17:30:52 ROUTER-MASTER dhcpd: uid lease 192.168.2.8 for client 24:a4:3c:40:a4:63 is duplicate on LAN2 May 19 17:56:17 ROUTER-MASTER dhcpd: uid lease 192.168.2.20 for client dc:9f:db:84:a8:51 is duplicate on LAN2 May 19 17:57:30 ROUTER-MASTER dhcpd: uid lease 192.168.2.9 for client 24:a4:3c:3e:40:d7 is duplicate on LAN2 May 19 18:03:49 ROUTER-MASTER dhcpd: uid lease 192.168.2.13 for client dc:9f:db:3e:f1:78 is duplicate on LAN2 May 19 19:18:08 ROUTER-MASTER dhcpd: uid lease 192.168.2.25 for client 24:a4:3c:4a:0b:67 is duplicate on LAN2 May 20 05:30:52 ROUTER-MASTER dhcpd: uid lease 192.168.2.8 for client 24:a4:3c:40:a4:63 is duplicate on LAN2 May 20 05:56:17 ROUTER-MASTER dhcpd: uid lease 192.168.2.20 for client dc:9f:db:84:a8:51 is duplicate on LAN2 May 20 05:57:30 ROUTER-MASTER dhcpd: uid lease 192.168.2.9 for client 24:a4:3c:3e:40:d7 is duplicate on LAN2 May 20 06:03:49 ROUTER-MASTER dhcpd: uid lease 192.168.2.13 for client dc:9f:db:3e:f1:78 is duplicate on LAN2 May 20 17:30:52 ROUTER-MASTER dhcpd: uid lease 192.168.2.8 for client 24:a4:3c:40:a4:63 is duplicate on LAN2 May 20 17:56:18 ROUTER-MASTER dhcpd: uid lease 192.168.2.20 for client dc:9f:db:84:a8:51 is duplicate on LAN2 May 20 17:57:30 ROUTER-MASTER dhcpd: uid lease 192.168.2.9 for client 24:a4:3c:3e:40:d7 is duplicate on LAN2 May 20 18:03:49 ROUTER-MASTER dhcpd: uid lease 192.168.2.13 for client dc:9f:db:3e:f1:78 is duplicate on LAN2
REPORTED:
Known Cause
One known situation where this can happen is documented in ISC bug ticket RT #26108. This is not a defect in the DHCP server code. In the scenario under consideration in ticket #26108, some clients may send DHCPDISCOVER or DHCPREQUEST packets with the seconds elapsed field coded as little endian, thus confusing the DHCP servers in a failover pair who are expecting this to be big endian. The incorrectly coded secs field may cause one server to incorrectly deduce that the other is not responding, and thus send a DHCPOFFER that it wouldn't normally. We've released a code workaround (available in 4.1-ESV-R8, 4.2.5 and newer) that may be helpful to some users:
Add a configure option, enable-secs-byteorder, to deal with clients that do the byte ordering on the secs field incorrectly. This field should be in network byte order but some clients get it wrong. When this option is enabled the server will examine he secs field and if it looks wrong (high byte non zero and low byte zero) swap the bytes. The default is disabled. This option is only useful when doing load balancing within failover.
[ISC-Bugs #26108]
Aside from any issues due to clients who don't set seconds elapsed field, or who are using a different endian setting, typically this behavior would only be observed where there is a high latency between the client and servers or where there are packet losses in the network causing the client to re-send the original packet with the secs field incremented.