network loop problem:flapping between port A and port B

[songnianzhou]

The switch log is as follows：

Aug 1 17:40:27.993: %SW_MATM-4-MACFLAP_NOTIF: Host 7423.44bd.c591 in vlan 114 is flapping between port Gi1/1/1 and port Gi1/0/24
Aug 3 16:56:01.779: %SW_MATM-4-MACFLAP_NOTIF: Host 7423.44bd.c591 in vlan 114 is flapping between port Gi1/1/1 and port Gi1/0/22
Aug 4 13:32:48.753: %SW_MATM-4-MACFLAP_NOTIF: Host 7423.44bd.c591 in vlan 114 is flapping between port Gi1/1/1 and port Gi1/0/22
Aug 8 14:39:56.429: %SW_MATM-4-MACFLAP_NOTIF: Host 7423.44bd.c591 in vlan 114 is flapping between port Gi1/1/1 and port Gi1/0/22
Aug 8 15:29:26.419: %SW_MATM-4-MACFLAP_NOTIF: Host 6014.b362.56f3 in vlan 114 is flapping between port Gi1/0/19 and port Gi1/0/7

 I have two questions.

1. First, vlan114 is a wireless network segment. The same problem I encountered before was caused by a loop in the wired network segment, but this time it is a wireless network segment, and it is impossible to have a loop.

2.Second, Is there a problem with the configuration of those APs connected to the AC controller?

I guess, since those MAC addresses are from the wireless scanner, whether the signal of the wireless scanner frequently switches between the two APs, and the two APs correspond to two different ports on the same switch, at this time both ports are on the same switch. There is the mac address of this wireless scanner, which causes the switch to think that a loop is generated.

Hope you can share the same problem or solution.

[balaji.bandi]

If this MAC belongs to a Wireless client, when the client roams, you see these error messages.

do you see any other issue other than Logs ?

[songnianzhou]

I can't tell if it happens during wireless roaming, i.e. switching between different APs, or under the same AP, all I can see is the log on the switch。

Fortunately, the network didn't matter, but I'd still like to troubleshoot where the problem is。

I'm currently checking whether there is a loop in the network, because we have more than 20 cisco switches connected to a lot of hubs, and it will take a while to check. It may be caused by the HUB loop, and need to continue to investigate

[MHM Cisco World]

""I can't tell if it happens during wireless roaming, i.e. switching between different APs, or under the same AP""
are  Gi1/1/1 and port Gi1/0/24 connect to AP shared same SSID ?

[songnianzhou]

As you said, all APs share one SSID, I'm not sure how this will affect.

Recently, I was investigating the problem of network loops. Since the loops do not occur frequently, they will occur once or twice in a few days or a few weeks. This makes it impossible for me to troubleshoot the loops. I can only troubleshoot all currently connected connections. HUB, no problem found so far.

I will keep updating my findings.

[songnianzhou]

To add, the setting parameters of the wireless controller。

Transition Time：5s

Scan Threshold:-72dbm minimum rssi:-85dbm

[songnianzhou]

Today's update: I found that all the ports that generate loops are connected to the AP. I haven't found any reason yet.

[MHM Cisco World]

all AP run same SSID 
and you not do site survey, 
the Client connect to AP-1 and then find AP-2 is stronger (because AP-1 and AP-2 close together), 
the client disconnect from AP-1 and connect to AP-2 
and when exchange data the SW detect that client Mac address is change from port AP-1 to port AP-2

this flapping conitous esspically if you have wireless client, or moving client. 
but this normal until you reach specific number then log message start to show. 

this what I think your issue. 

[songnianzhou]

As you said, using the wireless network client to switch between two APs that are very close together, and the two ports of the switch have this MAC at the same time, which causes a loop to appear in the log. Whether it is related to infinite roaming is still under investigation, because we The configuration of the wireless controllers in other bases of the company is the same, but the above situation does not occur. I went to the site to investigate the computer and did not encounter this situation. The scanner gun has this situation. The specific reason needs to be further confirmed.

Is it the problem of the scanner gun or the configuration of the wireless controller?

Since the simultaneous existence of MAC is a momentary thing, it is also difficult for me to judge.

I will keep updating my findings.