Provided are a computer program product, system, and method for updating zone information in a distributed switch of data forwarders. For each data forwarder, a sequence number is maintained for zone distribution messages sent to the data forwarder. A change to the ports in the network is detected comprising at least one of an allocation or deallocation of at least one port in the network. The sequence number for each data forwarder is incremented in response to detecting the change. For each data forwarder, a zone distribution message is generated indicating the at least one port allocated and/or deallocated, port information indicating each port in the network that may communicate with each other port, and the sequence number for the data forwarder. The generated zone distribution message is transmitted for each data forwarder to the data forwarder for which the zone distribution message was added.