I am trying to set up a firewall rule to block DHCP on an incoming port from a new sky router, unable to disable the DHCP server on router and I have my own DHCP on my server, when I select the port is says I cannot do it on a Slave use master, the port is part of a bridge with the other ports on the switch, I do not want to block DHCP on the whole bridge how can I do it, there is no way of using Master/Slave as on earlier versions of RouterOS
You should setup DHCP Snooping on that bridge: Bridging and Switching - RouterOS - MikroTik Documentation.
I will look in to that, looks complicated