Some embodiments of the invention provide a method for implementing a logical switching element that includes multiple logical ports through which the logical switching element receives and sends data packets. The method configures multiple managed forwarding elements to implement the logical switching element. The method also determines that port isolation has been enabled for the logical switching element. The method further provides a set of data directing the managed forwarding elements to drop a particular data packet received through a first logical port when the particular data packet is addressed to a second logical port different than the first logical port to implement the port isolation.