Enabling a fabric ISL
The fabric isl enable command controls whether an ISL should be formed between two cluster members. With the default setting of ISL discovery to auto and the ISL formation mode to enable , an ISL automatically forms between two cluster switches.
Performing a fabric isl enable command on an operational ISL has no effect. However, performing a no fabric isl enable command on an interface toggles its link status and subsequently disables ISL formation. In addition, the no fabric isl enable command triggers the switch to inform its neighbor that the local interface is ISL disabled. Upon receiving such information, a neighbor switch stops its ISL formation activity regardless of its current interface state.