My device is cisco Nexus 6001 Chassis (one unit dc switch)

# show version
kickstart: version 7.2(1)N1(1)
system:    version 7.2(1)N1(1)

I've configured mac move detection:

# conf t
# mac address-table notification mac-move
# logging level spanning-tree 6
# logging level fwm 6
# logging monitor 6

Looks like it is enabled:

 # show running-config | include move
 mac address-table notification mac-move
 # show logging level 
 Facility        Default Severity        Current Session Severity
 --------        ----------------        ------------------------
 fwm                     6                       6
 stp                     3                       6

But when I try to test this out (simply reconnect laptop on different ports of my switch), notifications are not sended to my logs.

The process of testing shown in picture:

enter image description here

Simply reconnecting between ports on downstream switches. The vlan is the same, so the mac is flaps between port on upstream NX-OS.

Maybe I've lost something important?

P.S. Maybe it is working when loop detection occurs. Old cisco 7600 spams log messages a lot if mac flaps between intefaces.

P.S. Maybe there is problem in negative numbers.

 # show mac address-table notification mac-move
 MAC Move Notify Triggers: 2814884
   Number of MAC Addresses added: -1214153019 
   Number of MAC Addresses moved: 0 
   Number of MAC Addresses removed: -1214196878 
  • At the point in time when you move the laptop (PC1) form SW1 to SW2, does the N6K still have a CAM table entry for PC1? Else it'll just be MAC learning when the first frame from PC1 arrives via SW2, and no mac move. – Marc 'netztier' Luethi Sep 5 '19 at 11:35
  • N6K seem to have a concept of limit/threshold and interval for mac-move notifications (see cisco.com/c/en/us/td/docs/switches/datacenter/nexus6000/sw/…) you may want to check if the given default values prevent syslog messages from being generated. – Marc 'netztier' Luethi Sep 5 '19 at 11:37
  • Yes it does have entry in CAM. – Tomato Sep 5 '19 at 12:06
  • I was reading about limits but there are no information that it need to be activated for mac-move. # show mac address-table notification threshold MAC Move Threshold : disabled , but on cisco 7600 show mac address-table notification threshold Status limit Interval disabled 50 120 it also disabled but working as expected. – Tomato Sep 5 '19 at 12:07
  • 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 '19 at 18:48

Physically moving a device from port to port will not trigger a mac-move event. When you disconnect from port A, the link drops and all state is discarded -- including any known MACs on that port. Similarly, when you (re)connect to port B, no previous state is known; there's no latent knowledge of where that MAC has previously been.

A mac-move event will only be triggered if a known MAC is seen on a port where it is not known to be. [currently in the CAM tables] (eg. a wireless client roaming between APs.) The purpose is to detect attempts at spoofing -- i.e. I claim to have the MAC of the exchange server and trick machines into sending me that traffic.

  • The main problem that I disconnect laptop from downstream switches. I've edit my post to help understand problem. – Tomato Sep 5 '19 at 6:09

The main problem is that mac move detection is workin a bit differently than on old IOS releases.

IOS every time drops log message when mac changes link where is nexus not. As the result mac move detection is exist and shows log message only when there are many flapping occurs between links. This is case where loops occur.

Generally I like old behaviour more than new one ;)

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