I have etherchannel configured between a 6500 and 2 separate 3750 switches using fibre links. One Port-channel is configured on 6500 ports gi1/11 & gi1/12 and is trunked with a single vlan allowed. It is connected to a 3750 with 2 corresponding ports configured in a port-channel. Another Port-channel is configured on 6500 ports gi1/13 & gi1/14 and is trunked with the same VLAN as before allowed. It is connected to another 3750 with 2 corresponding ports configure in a port-channel. When one of the fibres on the second port-channel is disconnected the whole etherchannel goes down, "show etherchannel summary" shows both interfaces as down. Channel group mode is "on", presume connected using PAGP. Why does the whole etherchannel go down, not just the disconnected link?