weird duplicate ip issue

Quiltface

Quiltface

Active Member
Was setting up some computers today (brand new network) and the 4 computers came online and 3 of them said something about duplicate ips on the network.... i double checked all their ips... ran a repair on them for good measure and a reboot. seemed to clear 2 of them up... but this other one (pc2) kept saying it... so i would unplug it and ping its ip... no reply...

check the ARP cache on my firewall and i notice that PC4's mac would be listed under its ip... 192.168.0.4 and pc2's 192.168.0.2.... so i cleared the arp cache and rebooted them... same thing but also a 5th computer would pop up... 192.168.0.5 which was not pingable.

looking at the arp table i would see a combination between PC4 having 192.168.0.4 & 192.168.0.2 or 192.168.0.4 & 192.168.0.5... same with pc2 it would either say 192.168.0.2 & 192.168.0.5 or just 192.168.0.2 or just .5

i even tried uninstalling the nics and reinstalling/ re-addressing them...

DHCP was disabled on the router/firewall so all pc's had static ips. none of the nics had dual ips and 192.168.0.5 was never pingable.


however when i changed the entire network to 192.168.1.0/24 none of this happened.... pc4 never fought with pc2 trying to get its ip and .5 never showed up again.

I am pretty much done with this as it is working now but I am wondering if I can get any ideas as to what might have been happening or if you had a similar experience
 
The only thing i can think of at the moment would be if you were running a modem/router combo unit and a separate router with dhcp enabled on both routers?
 
i had a uverse modem plugged into the untrusted port of my firewall and then a switch plugged into the trust with all the computers on it. there is dhcp on the uverse but a different subnet altogether... ther was dhcp enabled on the firewall at one point but i released all the IPs and disabled it after these duplicates happened. i even replaced the firewall with another one.... i banged my head on this for awhile today...

thanks for the input.
 
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