We have a very serious issue, which we cant seem to resolve. An uplink Fa0/1 port on out 3550 keeps going up/down 10-20 times a day for a few seconds. We tried changing switch without luck. Its is connected to a fiber running 4 km. The interface at the other end of the connection (from sh cdp neigh) does not go down. In the sh log output attached i tried making the switch in question spantree root on vlan 1 without luck. Also there is a sh int, and a sh int switchport.