A Port Remains In A Link Failure Or Not Connected State; An Unexpected Link Flapping Occurs - Cisco Nexus 9000 Series Troubleshooting Manual

Troubleshooting Ports
Problem
You cannot configure a
dedicated port.

A Port Remains in a Link Failure or Not Connected State

You may have a problem with ports or links becoming operational.
Problem
A port remains in a
link-failure state.

An Unexpected Link Flapping Occurs

When a port is flapping, it cycles through the following states, in this order, and then starts over again:
Possible Cause
The other three ports in the port group
are not shut down.
The port is not the first port in the port
group.
Possible Cause
The port connection is bad.
There is no signal because of a transit
fault in the small form-factor
pluggable (SFP), or the SFP may be
faulty.
The link is stuck in the initialization
state, or the link is in a point-to-point
state.
Cisco Nexus 9000 Series NX-OS Troubleshooting Guide, Release 7.x
A Port Remains in a Link Failure or Not Connected State
Solution
Use the shutdown command in interface
configuration mode to disable the other
three ports in the port group.
You can set only the first port in a port
group to the dedicated mode.
Solution
Verify the type of media in use. Is it
optical, single-mode (SM), or multimode
(MM)?
Use the shutdown command followed by
the no shutdown command to disable and
enable the port. If this problem persists, try
moving the connection to a different port
on the same or another module.
When this problem occurs, the port stays
in a transit port state and you see no signal.
There is no synchronization at the MAC
level. The problem might be related to the
port speed setting or autonegotiation.
Verify that the SFP on the interface is
seated properly. If reseating the SFP does
not resolve the issue, replace the SFP or
try another port on the switch.
Use the show logging command to check
for a "Link Failure, Not Connected system"
message.
Use the shutdown command followed by
the no shutdown command to disable and
enable the port. If this problem persists, try
moving the connection to a different port
on the same or another module.
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