Beginning with OS10.5.1.6, the default maximum transmission unit (MTU) size is 9216 bytes. Earlier versions default to 1512 bytes. When a SmartFabric is created, the default MTU for the switch is set to jumbo (9216 bytes), even if manually changed prior to creating the SmartFabric. This introduces the following behaviors:
- If the MTU is not individually set on a specific interface, the MTU is 9216 bytes.
- If the MTU has been specifically set on an individual interface, the MTU is the value that has been specified.
- If a FCoE VLAN is assigned to an interface, the MTU is set to 2500 bytes even if the MTU has been manually set to a different value before the FCoE VLAN was assigned. It is recommended that you set the MTU back to 9216 bytes after the FCoE VLAN is assigned.
See Configure Ethernet ports for instructions on setting the MTU.