Fibre Channel port masking

With Fibre Channel port masking, you control the use of Fibre Channel ports. You can control whether the ports are used to communicate to other nodes within the same local system, and if they are used to communicate to nodes in partnered systems. Fibre Channel port masking does not affect host or storage traffic. It gets applied only to node-to-node communications within a system and replication between systems.

Usefulness of Fibre Channel port masking

  • The setup of Fibre Channel port masks is useful when you have more than four Fibre Channel ports on any node in the system, as it saves setting up many SAN zones.
  • Fibre Channel I/O ports are logical ports, which can exist on Fibre Channel platform ports.
  • The system has two Fibre Channel port masks. The local port mask controls connectivity to other nodes in the same system, and the partner port mask control connectivity to nodes in remote, partnered systems. By default, all ports are enabled for both local and partner connectivity.
  • The port masks apply to all nodes on a system; a different port mask cannot be set on nodes in the same system. You do not have to have the same port mask on partnered systems.

What is Fibre Channel port masking

Port numbers refer to the Fibre Channel I/O port IDs that are shown by the lsportfc command.

A port mask is a string of zeros and ones. The last digit in the string represents port one. The previous digits represent ports two, three, and so on. If the digit for a port is 1, the port is enabled and the system attempts to send and receive traffic on that port. If it is 0, the system does not send or receive traffic on the port. If there are not sufficient digits in the string to specifically set a port number, the port is disabled for traffic.

For example, if the local port mask is set to 101101 on a node with eight Fibre Channel ports, ports 1, 3, 4 and 6 are able to connect with other nodes in the system. Ports 2, 5, 7 and 8 do not have connections. On a node in the system with only four Fibre Channel ports, ports 1, 3 and 4 are able to connect to other nodes in the system.

Note: The lsfabric CLI command shows all of the paths that are possible on the system (as defined by zoning) independent of their usage. Therefore, the command output includes paths that will not be used because of port masking.

The port masks are set by using the chsystem CLI command.