I want to configure the CRS125 so port one is uplink and all other ports are downlink. Basically port 1 can talk to any port but port 5 can only talk to port 1 for security. The PPPoE server will go on port 1 for example. So how would you set that up?
It would appear that you are talking about what is described in “port level isolation” here: http://wiki.mikrotik.com/wiki/Manual:CRS_examples
Does that seem like a starting point?