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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 5 Managing Switch Stacks
Troubleshooting Stacks

On a Catalyst 3750-E or 3750-X switch:

Switch# show platform stack ports buffer
Stack Debug Event Data Trace
==============================================================
Event type LINK: Link status change
Event type RAC: RAC changes to Not OK
Event type SYNC: Sync changes to Not OK
==============================================================
Event Stack Stack PCS Info Ctrl-Status Loopback Cable
Count Port IOS / HW length
========= ===== =================================== =========== ======== ========
Event type: LINK OK Stack Port 1
0000000014 1 FF01FF00 860204A7 5555FFFF 00000000 0CE60CA6 No /No 50 cm
0000000014 2 FF01FF00 85020823 AAAAFFFF 00000000 0CE60CA6 No /No 3 m
Event type: RAC
0000000015 1 FF01FF00 860204A7 5555FFFF 00000000 0CE60CA6 No /No 50 cm
0000000015 2 FF01FF00 85020823 AAAAFFFF 00000000 0CE60CA6 No /No 3 m
Event type: LINK OK Stack Port 2
0000000029 1 FF01FF00 860204A7 5555FFFF 00000000 1CE61CE6 No /No 50 cm
0000000029 2 FF01FF00 86020823 AAAAFFFF 00000000 1CE61CE6 No /No 3 m
Event type: RAC
0000000030 1 FF01FF00 860204A7 5555FFFF 00000000 1CE61CE6 No /No 50 cm
0000000030 2 FF01FF00 86020823 AAAAFFFF 00000000 1CE61CE6 No /No 3 m
Event type: LINK NOT OK Stack Port 1
0000009732 1 FF01FF00 00015B12 5555FFFF A49CFFFF 0C140CE4 No /No 50 cm
0000009732 2 FF01FF00 86020823 AAAAFFFF 00000000 0C140CE4 No /No 3 m
Event type: RAC
0000009733 1 FF01FF00 00015B4A 5555FFFF A49CFFFF 0C140CE4 No /No 50 cm
0000009733 2 FF01FF00 86020823 AAAAFFFF 00000000 0C140CE4 No /No 3 m
Event type: LINK NOT OK Stack Port 2
0000010119 1 FF01FF00 00010E69 25953FFF FFFFFFFF 0C140C14 No /Yes No cable
0000010119 2 FF01FF00 0001D98C 81AAC7FF 0300FFFF 0C140C14 No /No 3 m
Event type: RAC
0000010120 1 FF01FF00 00010EEA 25953FFF FFFFFFFF 0C140C14 No /Yes No cable
0000010120 2 FF01FF00 0001DA0C 81AAC7FF 0300FFFF 0C140C14 No /No 3 m
Finding a Disconnected Stack Cable

Stack cables connect all stack members. Port 2 on Switch 1 connects to Port 1 on Switch 2.

This is the port status for the members:

Switch# show switch stack-ports summary
Switch#/ Stack Neighbor Cable Link Link Sync # In
Port# Port Length OK Active OK Changes Loopback
Status To LinkOK
-------- ------ -------- -------- ---- ------ ---- --------- --------
1/1 OK 2 50 cm Yes Yes Yes 0 No
1/2 OK 2 50 cm Yes Yes Yes 0 No
2/1 OK 1 50 cm Yes Yes Yes 0 No
2/2 OK 1 50 cm Yes Yes Yes 0 No

If you disconnect the cable from Port 2 on Switch 1, these messages appear:

%STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 2 has changed to state DOWN
%STACKMGR-4-STACK_LINK_CHANGE: Stack Port 2 Switch 1 has changed to state DOWN

This is now the port status:

Switch# show switch stack-ports summary