Adding a new network device may cause the problem, eg by default all devices are vtp server mode, hence adding new device will overwrite all the vlans if the revision number of new added device is higher than the previous vtp server.Sent from Cisco T...
Often the duplex mismatch causes slow in network speed and runts, it is important to have the same duplex setting at both ends which may be the reason of CRC errorsSent from Cisco Technical Support iPhone App