09-12-2020 11:49 PM
I am getting a MAC Flap every ~15 seconds.
But reviewing the network layout, it's physically impossible for this to happen.
What could be causing this?!
09-13-2020 12:18 AM
- Depends, the mac address could for instance network or 'cluster redundancy' for 2 similar devices on the different ports.
M.
09-13-2020 12:43 AM
We have nothing fancy like that....
09-13-2020 02:19 AM
- Scrutinize the network settings/adapters/mac-addresses from the involved devices in detail.
M.
09-13-2020 02:47 AM - edited 09-13-2020 02:49 AM
Is this the only MAC address causing the issue?
What is the client?
What is connected to Fa0/4?
What is connected to Fa0/5?
09-13-2020 03:17 AM
At the moment, yes. But I have seen other MAC addresses flap over to fa0/5.
The one in RED is not located in the same physical location. It is 57kms away connected over a series of switches, eventually entering the Cisco switch on port Fa0/4.
So how can the Cisco switch think it is appearing on Fa0/5? It is PHYSICALLY not possible.
Every few seconds, show mac address-table address 0009.0bf0.56b8 is showing the port is on Fa0/4 then on Fa0/5.
So what else can cause Cisco to say 'MAC Flap'? How could a device 'appear' on another port there is no way it could be on?
09-13-2020 03:21 AM - edited 09-13-2020 03:23 AM
I think you need to go to the site and visually inspect the path. I suspect someone has put an un-managed switch there without you knowing.
Another thing, how many MAC address can be seen from Fa 0/5 (sh mac address interface Fa0/5)?
09-13-2020 03:25 AM
There is an unmanaged switch there. 57kms away. Physically not possible to get on to Fa0/5.
09-13-2020 03:59 AM
Well, if you are saying both Fa0/4 and Fa0/5 is connected to a downstream client (and not an un-managed switch or a hub) then the output to the command "sh mac address interface Fa0/4" and "sh mac address interface Fa0/5" should be short.
09-13-2020 04:44 AM - edited 09-13-2020 04:50 AM
This is Fa0/5. It is connected to LAN0 of a Wi-MAX station, which then communicates to a Wi-MAX AP. The one in RED is the one flapping. It is physically located 57kms away, over 4 Hirschmann switches connected via fiber optic links.
Fa0/4 is connected to a HUGE number of devices via several Hirschmann switches and fiber optic links to locations many kilometers away.
My point is. There is absolutely no way something is bridging/linked between Fa0/4 and Fa0/5. I've checked. Absolutely impossible.
09-13-2020 04:53 AM
Ok, so what is the output to the command "sh mac add interface F0/4"?
09-13-2020 04:58 AM
SACRL201#sh mac add interface F0/4 Mac Address Table ------------------------------------------- Vlan Mac Address Type Ports ---- ----------- -------- ----- 195 0009.0bf0.44a2 DYNAMIC Fa0/4 195 0009.0bf0.44a4 DYNAMIC Fa0/4 195 0009.0bf0.56b8 DYNAMIC Fa0/4 195 0009.0bf0.58f4 DYNAMIC Fa0/4 195 0009.0bf0.591a DYNAMIC Fa0/4 195 0009.9100.ef7a DYNAMIC Fa0/4 195 0009.9100.ef7d DYNAMIC Fa0/4 195 0009.9101.138a DYNAMIC Fa0/4 195 0009.9101.6579 DYNAMIC Fa0/4 195 0009.9101.65af DYNAMIC Fa0/4 195 0009.9101.cee0 DYNAMIC Fa0/4 195 0009.9102.097c DYNAMIC Fa0/4 195 0009.9102.347f DYNAMIC Fa0/4 195 0009.9102.3480 DYNAMIC Fa0/4 195 0009.9102.3481 DYNAMIC Fa0/4 195 0009.9102.3482 DYNAMIC Fa0/4 195 0009.9102.3bc6 DYNAMIC Fa0/4 195 0009.9103.a78a DYNAMIC Fa0/4 195 0009.9103.a78b DYNAMIC Fa0/4 195 0009.9104.90e5 DYNAMIC Fa0/4 195 0009.9107.6e64 DYNAMIC Fa0/4 195 0009.9107.6e69 DYNAMIC Fa0/4 195 0009.9140.c856 DYNAMIC Fa0/4 195 0009.9140.c861 DYNAMIC Fa0/4 195 0009.9140.cebb DYNAMIC Fa0/4 195 0009.9140.db36 DYNAMIC Fa0/4 195 0009.9140.db46 DYNAMIC Fa0/4 195 0009.9140.dca9 DYNAMIC Fa0/4 195 0009.9140.dda1 DYNAMIC Fa0/4 195 0009.9140.dda2 DYNAMIC Fa0/4 195 0009.9140.ddb3 DYNAMIC Fa0/4 195 0009.9140.ddbb DYNAMIC Fa0/4 195 0009.9141.4375 DYNAMIC Fa0/4 195 0009.9141.5c10 DYNAMIC Fa0/4 195 0009.9141.5c26 DYNAMIC Fa0/4 195 0009.9141.6b57 DYNAMIC Fa0/4 195 0009.9141.86d8 DYNAMIC Fa0/4 195 0009.9141.86e4 DYNAMIC Fa0/4 195 0009.9144.56cc DYNAMIC Fa0/4 195 0009.9144.56fb DYNAMIC Fa0/4 195 0009.9144.5753 DYNAMIC Fa0/4 195 0009.9144.5778 DYNAMIC Fa0/4 195 000d.8d01.bf68 DYNAMIC Fa0/4 195 000d.8d01.d8ba DYNAMIC Fa0/4 195 000d.8d01.d8c2 DYNAMIC Fa0/4 195 000d.8d01.d8c6 DYNAMIC Fa0/4 195 000f.fede.8825 DYNAMIC Fa0/4 195 0011.322f.ee90 DYNAMIC Fa0/4 195 0013.21b0.8fbe DYNAMIC Fa0/4 195 001d.7f00.07e7 DYNAMIC Fa0/4 195 0020.4a06.6548 DYNAMIC Fa0/4 195 0020.4a06.657a DYNAMIC Fa0/4 195 0020.4a06.bde7 DYNAMIC Fa0/4 195 0020.4a06.c08f DYNAMIC Fa0/4 195 0020.4a06.c85b DYNAMIC Fa0/4 195 0020.4a06.c982 DYNAMIC Fa0/4 195 0020.4a09.fa1f DYNAMIC Fa0/4 195 0020.4a09.fa27 DYNAMIC Fa0/4 195 0020.4a09.faae DYNAMIC Fa0/4 195 0020.4a09.fb58 DYNAMIC Fa0/4 195 0020.4a0a.1ce8 DYNAMIC Fa0/4 195 0020.4a34.29dc DYNAMIC Fa0/4 195 0020.4a34.29e1 DYNAMIC Fa0/4 195 0020.4a34.754d DYNAMIC Fa0/4 195 0020.4a34.7603 DYNAMIC Fa0/4 195 0020.4a69.ee85 DYNAMIC Fa0/4 195 0020.4a69.eea1 DYNAMIC Fa0/4 195 0080.6306.3ffd DYNAMIC Fa0/4 195 0080.6306.4018 DYNAMIC Fa0/4 195 0080.6306.404e DYNAMIC Fa0/4 195 0080.6306.4069 DYNAMIC Fa0/4 195 0080.6306.4084 DYNAMIC Fa0/4 195 0080.6306.45ad DYNAMIC Fa0/4 195 0080.6306.45b7 DYNAMIC Fa0/4 195 0080.6306.45c1 DYNAMIC Fa0/4 195 0080.6319.5ed8 DYNAMIC Fa0/4 195 0080.6348.c3d8 DYNAMIC Fa0/4 195 0080.6368.f13e DYNAMIC Fa0/4 195 0080.6379.ff80 DYNAMIC Fa0/4 195 0080.6379.ffa8 DYNAMIC Fa0/4 195 0080.6379.ffbc DYNAMIC Fa0/4 195 0080.6379.ffd0 DYNAMIC Fa0/4 195 0080.6386.e919 DYNAMIC Fa0/4 195 0090.e854.db16 DYNAMIC Fa0/4 195 00a0.45b3.3310 DYNAMIC Fa0/4 195 3c52.8268.b53b DYNAMIC Fa0/4 195 3c52.8268.f7d6 DYNAMIC Fa0/4 195 3c52.826a.1da1 DYNAMIC Fa0/4 195 3c52.8271.6a5d DYNAMIC Fa0/4 195 3c52.8271.6dfa DYNAMIC Fa0/4 195 3c52.8274.92ae DYNAMIC Fa0/4 195 509a.4c2b.ea49 DYNAMIC Fa0/4 195 509a.4c2b.eac7 DYNAMIC Fa0/4 195 509a.4c2b.ebfb DYNAMIC Fa0/4 195 509a.4c2b.ec3c DYNAMIC Fa0/4 195 509a.4c2c.37f9 DYNAMIC Fa0/4 195 509a.4c2c.389c DYNAMIC Fa0/4 195 6400.6a7c.e304 DYNAMIC Fa0/4 195 ec74.ba0c.c8ae DYNAMIC Fa0/4 195 ec74.ba11.27ad DYNAMIC Fa0/4 195 ec74.ba11.27c1 DYNAMIC Fa0/4 195 ec74.ba3f.f785 DYNAMIC Fa0/4 195 ec74.baca.f40e DYNAMIC Fa0/4 195 ec74.baca.f422 DYNAMIC Fa0/4 195 ece5.5583.d346 DYNAMIC Fa0/4 195 ece5.5583.d396 DYNAMIC Fa0/4 195 ece5.5583.d486 DYNAMIC Fa0/4 195 ece5.55cf.b4d6 DYNAMIC Fa0/4 195 f8b1.56b3.8b17 DYNAMIC Fa0/4 195 f8b1.56b3.b7d5 DYNAMIC Fa0/4 Total Mac Addresses for this criterion: 110
You can see the offending MAC in this list.
If I perform the command again, seconds later, it will have disappeared.
09-13-2020 05:17 AM
Is there another WiMAX connected to Fa0/4?
09-13-2020 05:32 AM
Nope. Fa0/4 connects ONLY to a Hirschmann managed switch as seen in my picture above. There are no WiMAX stations on this link.
There is no physical relation between Fa0/4 and Fa0/5.
It's not the first time I've seen MAC Flapping being reported with Fa0/5. It's just never been this bad, with one MAC address, every few seconds. It's like the Ubiquiti NanoM5 hates Cisco...
09-13-2020 06:07 AM
Hmmm... I'm trying to understand what I am seeing....
This is the one that is connected to Fa0/5. You can see the offending MAC is the only one listed as WLAN0...
What is this BRIDGE table... And why is the BRIDGE table on all of these WIMAX stations showing ALL the devices that are located on Fa0/4...?
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