Several time ago I've foud that NX-OS sends STM_LEARNING_OVERLOAD

EET: %FWM-4-STM_LEARNING_OVERLOAD: system experiencing unusual number of new address notifications - deferring learn notification for 120 seconds

After this message cisco floods traffic to all ports.

The main problem I can't find the source besause this is only message I get. No loops are detected so I can't further to investigate problem.

Is there some additional commands that help to debug this problem. Mac move detection is activated:

# show running-config | include mac
mac address-table notification mac-move

Can someone please tell. When I issue detail command - is there interface (in this case 1/38) which can cause problem?

# show spanning-tree active detail 

 MST0000 is executing the mstp compatible Spanning Tree protocol
 Bridge Identifier has priority 4096, sysid 0, address 002a.6a60.d101
 Configured hello time 2, fex hello time 12, max age 20, forward delay 15
 We are the root of the spanning tree
 Topology change flag not set, detected flag not set
 Number of topology changes 1039 last change occurred 0:14:24 ago
      from Ethernet1/38
 Times:  hold 1, topology change 35, notification 2
      hello 2, max age 20, forward delay 15 
 Timers: hello 0, topology change 0, notification 0

P.P.S. Switch software version:

  BIOS:      version 2.0.0
  Power Sequencer Firmware: 
             Module 1: v4.0
             Module 1: v4.0
  Fabric Power Sequencer Firmware: Module 1: version v4.0
  Microcontroller Firmware:        version v1.2.0.5
  QSFP Microcontroller Firmware:   
             Module 1: v1.3.0.0
  CXP Microcontroller Firmware:   
             Module not detected
  kickstart: version 7.2(1)N1(1)
  system:    version 7.2(1)N1(1)
  BIOS compile time:       12/19/2014
  kickstart image file is: bootflash:///n6000-uk9-kickstart.7.2.1.N1.1-new.bin
  kickstart compile time:  10/14/2015 19:00:00 [10/15/2015 09:02:08]
  system image file is:    bootflash:///system_7_2_1_N1_1_ipsada.bin
  system compile time:     10/14/2015 19:00:00 [04/10/2016 11:51:48]

  cisco Nexus 6001 Chassis ("Nexus 64 Supervisor")
  • What code version are you running on the N6K? Also - how long has it been since counters were cleared? 1039 topology changes might be nothing significant if the switch has been up for years but is most definitely a problem if that number accrued in ten minutes.
    – rnxrx
    Oct 2, 2019 at 3:20
  • version 7.2(1)N1(1) I added info to main question. Counters where never cleared.
    – Tomato
    Oct 2, 2019 at 4:15
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin
    Dec 15, 2019 at 19:31

2 Answers 2


I found that this is mailnly STP configuration issue on downstream switches.

First of all we should verify all STP configuration on all access switches (EdgePort stp name etc.)


This message will shown when your MAC address learning is overloaded. (And it should be gets ok after 120 seconds!) . If you disconnect all the cables connect to switch and you still see this syslog message. Then it is a bug. See this link

  • I know about this bug, but I have different device and software release.
    – Tomato
    Oct 2, 2019 at 6:08
  • Can you disconnect all ports from switch and test it ?
    – Mahdi
    Oct 2, 2019 at 6:11
  • Unfortunately not, this is production switch.
    – Tomato
    Oct 2, 2019 at 7:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.