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ILPOWER-5-SINGLE_PAIRSET_FAULT: Interface Gi1/0/24: shutting down Alt-A pairset due to DISCONNECT fault

This may be a somewhat unique environment that we are experiencing this problem. We are developing a PoE tester and after many iterations of PoE negotiations, this error will appear. Once this error appears, the port will no longer succeed when we attempt to negotiation again for PoE.


Does anyone have more information on what the critical fault actually is in this scenario? From Cisco documentation:


%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/1, changed state to up
%ILPOWER-5-SINGLE_PAIRSET_FAULT: Interface Gi1/0/1: shutting down Alt-B pairset due to OVERCLS fault
%ILPOWER-5-SINGLE_PAIRSET_FAULT: Interface Gi1/0/1: shutting down Alt-B pairset due to OVERCLS fault

This error means that the dual signature powered device on the switchport has hit a critical fault on one pairset and hence that pairset will be shutdown. Example above is taken from a UPoE+ capable powered device & switch.

This doesn't give any insight into what DISCONNECT means in the above scenario unforunately.

Leo Laohoo
VIP Community Legend

What switch model number?


Leo Laohoo
VIP Community Legend

Do the following: 

test cable tdr interface Gi1/0/1

Wait for approximately 60 seconds for the test to run. 

show cable tdr interface Gi1/0/1

And then post the complete output from the last command.

Happy to run the command and provide the output once I'm able to reproduce this setup. I will update w/ a reply once this is possible!


I'll provide a bit more information- we can do thousands of PoE negotiations with this switch without any problem, but once we begin utilizing LLDP for PoE negotiations, after a varying amount of runs the switch will show this error.


I'm really looking for more information on what exactly this DISCONNECT problem is referring to with regards to PoE.



Cisco-C9404R-Class8#show cable tdr interface Gi1/0/24
TDR test last run on: October 16 08:47:56

Interface   Speed Local pair Pair length        Remote pair Pair status
---------   ----- ---------- ------------------ ----------- --------------------
Gi1/0/24    1000M Pair A     10   +/- 10 meters Pair A      Normal
                  Pair B     9    +/- 10 meters Pair B      Normal
                  Pair C     9    +/- 10 meters Pair C      Normal
                  Pair D     9    +/- 10 meters Pair D      Normal
Leo Laohoo
VIP Community Legend

TDR output looks good. 

@bschaefe wrote:

once we begin utilizing LLDP for PoE negotiations

Wait ... LLDP?   

IOS-XE, 3.650/3850 and Catalyst 9k, do not like LLDP and CDP running simultaneously.  Unlike "classic" IOS, which LLDP and CDP can work harmoniously, if LLDP is required then CDP must be disabled on each port/interface.

Unforunately, this didn't have any positive affect. Disabled CDP on both the Cisco9404 interface and our device, and the same error occured after a while of repeatedly doing PoE negotiations.
Leo Laohoo
VIP Community Legend

What firmware is the chassis running on?

Cisco-C9404R-Class8#show version
Cisco IOS XE Software, Version 16.12.02
Cisco IOS Software [Gibraltar], Catalyst L3 Switch Software (CAT9K_IOSXE), Version 16.12.02, RELEASE SOFTWARE (fc2)
Technical Support:
Copyright (c) 1986-2019 by Cisco Systems, Inc.
Compiled Tue 19-Nov-19 10:04 by mcpre
Leo Laohoo
VIP Community Legend

Hmmmm ... 16.12.2. 

May I ask if it is possible to upgrade to 16.12.4?  If it is possible, may I also ask that the chassis have a COLD REBOOT (instead of the "reload" command)?

NOTE:  COLD REBOOT is physically powering down the entire chassis, wait for 5 seconds and then powering the chassis back up.

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