Core issue
The %GIGASTACK-1-NO_LOOP_DETECT message indicates the link neighbor of link [dec] of GigaStack GBIC in [chars] did not respond to the loop detection request. If loop topology is deployed, make sure all switches in the stack are running the latest software.
This message means that no acknowledgement for the loop-detection request is received from one of the links on a GigaStack GBIC module. Either the neighboring switch does not support the GigaStack GBIC loop-breaking algorithm, or the link between the two GigaStack GBIC modules is broken. In this condition, a GigaStack loop topology is not automatically detected, and the connectivity between switches in the stack can be lost. [dec] is the link number, and [chars] is the slot number.
Resolution
If a loop topology is used with the GigaStack GBIC module, ensure that the latest software is running on all switches in the stack. Check the GigaStack GBIC modules involved to ensure that they are functioning.
Gigastack can work only in half duplex. For more information, refer to the Features section of Catalyst GigaStack GBIC.
