28 Fabric OS Troubleshooting and Diagnostics Guide
53-1002150-02
Link failures
3
Link failures
A link failure occurs when a server, storage, or switch device is connected to a switch, but the link
between the devices does not come up. This prevents the devices from communicating to or
through the switch.
If the switchShow command or LEDs indicate that the link has not come up properly, use one or
more of the following procedures.
The port negotiates the link speed with the opposite side. The negotiation usually completes in one
or two seconds; however, sometimes the speed negotiation fails.
Determining a successful speed negotiation
Skip this procedure if the port speed is set to a static speed through the portCfgSpeed command.
1. Enter the portCfgShow command to display the port speed settings of all the ports.
2. Enter the switchShow command to determine if the port has module light.
3. Enter the portCfgSpeed command to change the port speed to 1, 2, 4 or 8 Gbps, depending on
what speed can be used by both devices. This should correct the negotiation by setting to one
speed.
4. Enter the portLogShow or portLogDump command.
5. Check the events area of the output:
time task event port cmd args
-----------------------------------------------------------------
14:38:51.976 SPEE
sn
<Port#>
NC
00000001,00000000,00000001
14:39:39.227 SPEE
sn
<Port#>
NC
00000002,00000000,00000001
• In the event column, sn indicates a speed negotiation.
• In the cmd column, NC indicates the negotiation has completed.
If these fields do not appear, proceed to the step 6.
6. Correct the negotiation by entering the portCfgSpeed [slotnumber/]portnumber, speed_level
command if the fields in step 5 do not appear.
switch:admin> portcfgspeed
Usage: portCfgSpeed PortNumber Speed_Level
Speed_Level: 0 - Auto Negotiate
1 - 1Gbps
2 - 2Gbps
4 - 4Gbps
8 - 8Gbps
ax - Auto Negotiate + enhanced retries
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