Identifying Loopback Problems; Software Loopback - Cisco Catalyst 2975 Software Configuration Manual

Chapter 6 Managing Switch Stacks
Table 6-5
Field
# Changes to LinkOK
In Loopback

Identifying Loopback Problems

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•
•
•
•
•

Software Loopback

In a stack with three members, stack cables connect all the members.
Switch# show switch stack-ports summary
Switch#/
Port#
--------
1/1
1/2
2/1
2/2
3/1
3/2
If you disconnect the stack cable from Port 1 on Switch 1, these messages appear:
01:09:55: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 2 Switch 3 has changed to state DOWN
01:09:56: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 1 has changed to state DOWN
Switch# show switch stack-ports summary
Switch#/
Port#
--------
1/1
1/2
2/1
2/2
3/1
3/2
OL-19720-02
show switch stack-ports summary Command Output (continued)
Description
This shows the relative stability of the link.
If a large number of changes occur in a short period of time, link flapping
can occur.
Software Loopback, page 6-25
Software Loopback Example: No Connected Stack Cable, page 6-26
Software Loopback Examples: Connected Stack Cables, page 6-26
Hardware Loopback, page 6-27
Hardware Loopback Example: LINK OK event, page 6-27
Hardware Loop Example: LINK NOT OK Event, page 6-28
Stack Neighbor
Port
Status
------ --------
OK 3
OK 2
OK 1
OK 3
OK 2
OK 1
Stack Neighbor
Port
Status
------ --------
Absent None
OK 2
OK 1
OK 3
OK 2
Down None
No—At least one stack port on the member has an attached stack
•
cable.
Yes—None of the stack ports on the member has an attached stack
•
cable.
Cable Link Link
Length OK Active
-------- ---- ------
50 cm Yes Yes
3 m Yes Yes
3 m Yes Yes
50 cm Yes Yes
50 cm Yes Yes
50 cm Yes Yes
Cable Link Link
Length OK Active
-------- ---- ------
No cable No No
3 m Yes Yes
3 m Yes Yes
50 cm Yes Yes
50 cm Yes Yes
50 cm No No
Catalyst 2975 Switch Software Configuration Guide
Troubleshooting Stacks
Sync # In
OK Changes Loopback
To LinkOK
---- --------- --------
Yes 1 No
Yes 1 No
Yes 1 No
Yes 1 No
Yes 1 No
Yes 1 No
Sync # In
OK Changes Loopback
To LinkOK
---- --------- --------
No 1 No
Yes 1 No
Yes 1 No
Yes 1 No
Yes 1 No
No 1 No
6-25