False positives with dhcp-snooping server-guard on 4210

[vasek125]

Hello, I upgraded firmware on my 3com 4210 switches to the latest version and enabled dhcp-snooping server-guard function so the switch will disable port in case of the dhcp server is found.

configuration on monitored ports:

dhcp-snooping server-guard enable
dhcp-snooping server-guard method shutdown

This function is not working properly. Some computers (20 identical lenovo laptops) sometimes cause to shutdown switch port because of dhcp snooping function. But there is no dhcp server on these laptops. Where is the problem? How can I fix it? ... or must I disable dhcp-snooping method shutdown?