Hello,
We have implemented 802.1x on our network. Problem is with computers that have DHCP reservation. With those computers, that is “escalation” problem.
We have VALID DHCP reservation for several computers, and it works, but few times a week those computers do not get IP address, usually at the client side we gat address conflict with ip 0.0.0.0 and mac address is CISCO vendor, but we can not determent which or what device.
I know that when computer get IP address and before it assignee that address it try’s with ARP broadcast if that address is already used.
When that happened, I get NACK event. Problem is that WHEN it happens, it fills up DHCP client long in a few seconds., the same happened ad DHCP server.
I have setup wireshark to listen only for DHCP Server, and everything look ok. Now i`m in a process to setup monitoring on client side, to capture what is happening,
Interesting is that DGCP reservation fro that client change when NACK happed It change from VALID client MAC address to .We have to basically recreate reservation, or client does not get IP address it will get APIPA. Strange is that even if we reboot client PC several times, it will not get any valid IP address from DHCP scope, only APIPA.
We have setup to IP helpers, but we have ONLY one DHCP server. Alll servers (2008 R2)are up to date and the same is with clients (Windows 7).
What could be problem ?