Link Flapping - Cisco Nexus 1000V Troubleshooting Manual

Chapter 9 Ports

Link Flapping

When you are troubleshooting unexpected link flapping, it is important to have the following
information:
•
•
•
Possible Cause
The bit rate exceeds the
threshold and puts the port
into an error-disabled state.
A hardware failure or
intermittent hardware error
causes a packet drop in the
switch.
A software error causes a
packet drop.
A control frame is erroneously
sent to the device.
ESX errors, or link flapping,
occurs on the upstream switch.
OL-31593-01
Who initiated the link flap.
The actual reason for the link being down.
For a definition of link flapping, see the "Link Flapping" section on page
Solution
Disable and then enable the port.
shut
no shut
The port should return to the normal state.
An external device might choose to initialize the link again when
encountering the error. If so, the exact method of link initialization
varies by device.
Determine the reason for the link flap as indicated by the MAC
1.
driver.
Use the debug facilities on the end device to troubleshoot the
2.
problem.
Use the troubleshooting guidelines in the documentation for your
ESX or upstream switch.
Cisco Nexus 1000V Troubleshooting Guide, Release 5.2(1)SV3(1.1)
Problems with Ports
9-5.
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