I got two errors showing up on console: (1) 4w5d: %LINK-4-ERROR: FastEthernet0/3 is experiencing errors (2) 4w5d: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on FastEthernet0/16 (20), with Switch3 FastEthernet0/48 (1). Also, one port on one of the switch is flapping. There are there switches on this rack connected by both fiber and crossover cable. How can I fix these problems. Thanks.