I can see in my network any customer can communicate to any one on the same VLAN. Basically when ever any unknown packets ingress into the switch. Switch found no record in CAM table, so that frame flood every port of the respected VLAN, except the frame received port. Such a communication can very dangerous for the service provider and its customer. Because any one can sniff or send information to other customer in same VLAN.
Broadcast packet also flooded into the network that can bottleneck our network. The way to protect such a bottleneck of the network we can configure switch port as protected port thus no port can directly communicated in a same broadcast domain.
switchchport mode access
switchport access vlan 30
This way we can protect the user in same VLAN. Protected port only be configured in edge port not the trunk port or L3 connected port. Now the protected port prevent any unicast, broadcast or multicast packet entering to the same switch interface. But traffic forwarded to same domain can be communicated through L3 device like router.