How to block other DHCP server in my network?

Question

Hello, 
 I'm new to Sophos Community and user. 
 Today i faced a problem that someone inside my network reset an access point and its default setting enabled DHCP, so all devices get IP from access point. 
 can anyone help me.

lferrara · Answer

Peter this an issue that a firewall cannot managed if the network is flat. 
 XG can block the dhcp requests if they traverse the firewall (layer 3) but if your computers get an ip from a dhcp in the same LAN you have to use other mechanisms to block rogue dhcp servers (nac for example and training your users). 
 Regards