I had a problem this week in the network. A host was plugged in the network with the same IP address of the default gateway of that Vlan.
Is there someway to prevent it? I know with 802.11x I could know who is doing that, but it would not avoid the problem to occur.
Is there anyway to force the hosts to use DHCP or something?
It will also prevent an unauthorised DHCP server on an untrusted interface. It ensures (on an untrusted interface) only DHCP client messages such as DHCP requests (denies DHCP server messages such as DHCP replies) and only allows source IP addresses from packets that it knows have been assigned by DHCP. Does that make sense?