- Bronze, 100 points or more
i find various reasons for a port to go into erridisable state such as pagp,late-collision,port securiy etc. But i did not find that port can go into errdisable state for duplex mismatch.
Rather the port stays up,showing excessive collision,runt etc.
am i correct? In cisco press book(bscmsn) by David Hucaby,various reasons are listed for the port to go into errdisable state.There is no duplex mismatch reason among them.
can a port go into errdisable state for duplex mismatch reason?
thanks a lot!
Sure, duplex mismatch can cause the interface to go into an error disable state.
quoting from CCO:
Duplex mismatches are common because of failures to autonegotiate speed and duplex properly. Unlike a half duplex device, which must wait until there are no other devices that transmit on the same LAN segment, a full-duplex device transmits whenever the device has something to send, regardless of other devices. If this transmission occurs while the half-duplex device transmits, the half-duplex device considers this either a collision (during the slot time) or a late collision (after the slot time). Because the full-duplex side never expects collisions, this side never realizes that it must retransmit that dropped packet. A low percentage rate of collisions is normal with half duplex but is not normal with full duplex. A switch port that receives many late collisions usually indicates a duplex mismatch problem. Be sure that the ports on both sides of the cable are set to the same speed and duplex. The show interfaces interface_number command tells you the speed and duplex for Catalyst switch ports. Later versions of Cisco Discovery Protocol (CDP) can warn you about a duplex mismatch before the port is put in the error-disabled state.""