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8-22
Cisco MDS 9000 Family Troubleshooting Guide, Release 3.x
OL-9285-05
Chapter 8 Troubleshooting Ports
Common Problems with Port Interfaces
Table 8-5 lists possible causes and solutions for link flapping.
Note We recommend that you do not disable and then enable a T or TE port. This would affect all the VSANs
crossing the EISL instead of just the VSAN experiencing the problem.
Table 8-5 Unexpected Link Flapping Occurs
Symptom Possible Cause Solution
Unexpected link
flapping occurs.
The bit rate exceeds the threshold and puts the port
into an error disabled state.
Right-click the port in Device Manager and select
disable and then enable, or use the shut CLI
command followed by the no shut command to
return the port to the normal state.
The switch cannot complete the link reset. The
link reset protocol failure results in a link flap that
may be the result of:
• The input buffer did not become empty within
the link reset timeout period.
• The link partner did not respond to a link reset
initiated by the switch.
The switch initiates the link reset when all credits
are lost for more than four seconds or when there
is a temporary signal or sync loss condition that
lasts for less than 100msec. See the
“Troubleshooting Port Problems” section on
page 8-15 to verify this condition.
Right-click the port in Device Manager and select
disable and then enable, or use the shut CLI
command followed by the no shut command to
disable and enable the port. If this does not clear
the problem, try moving the connection to a
different port on the same or another module.
There is a credit loss condition on an FL port. When credit loss or a transmit stuck condition is
detected in the FL port, the FC-MAC drive flaps
the link as a recovery process. See the
“Troubleshooting Port Problems” section on
page 8-15.
Some problem in the switch triggers the link flap
action by the end device. Some of the causes are:
• Packet drop in the switch, because of either a
hardware failure or an intermittent hardware
error such as X-bar sync loss.
• Packet drop resulting from a software error.
• A control frame is erroneously sent to the
device.
Determine link flap reason as indicated by the
MAC driver. Use the debug facilities on the end
device to troubleshoot the problem. An external
device may choose to reinitialize the link upon
encountering the error. In such cases, the exact
method of reinitializing the link varies by device.
See the “Troubleshooting Port Problems” section
on page 8-15 for more information on externally
triggered link flaps.
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