Error Disable recovery on layer 2 loop SW_MATM-4-MACFLAP_NOTIF

[paul amaral]

Hi, recently I had an issue where a mac address was flapping between two sites that are connected via a Port-channel trunk, see logs below. I determined/assume it went into err-disable state because of a spanning tree loop as our intermediary provider was having issues. What am trying to understand is if there is  a way to recover from this error.

Under errdisable recovery I don’t see anything pertaining to STP or Layer 2 loops. I wanted to know if there’s a way to recover from this mac flapping error or layer 2 loop which am assuming is due to a Spanning tree loop.

3600-Stack-SW#sh errdisable recovery
ErrDisable Reason            Timer Status
-----------------            --------------
arp-inspection               Disabled
bpduguard                    Disabled
channel-misconfig            Disabled
dhcp-rate-limit              Disabled
dtp-flap                     Disabled
evpn-mh-core-isolation       Disabled
gbic-invalid                 Disabled
inline-power                 Disabled
l2ptguard                    Disabled
link-flap                    Enabled
mac-limit                    Disabled
link-monitor-failure         Disabled
loopback                     Disabled
oam-remote-failure           Disabled
pagp-flap                    Disabled
port-mode-failure            Disabled
pppoe-ia-rate-limit          Disabled
psecure-violation            Disabled
security-violation           Disabled
sfp-config-mismatch          Disabled
storm-control                Disabled
udld                         Disabled
psp                          Disabled
dual-active-recovery         Disabled
evc-lite input mapping fa    Disabled
Recovery command: "clear     Disabled
mrp-miscabling               Disabled

Dec  6 21:34:20 est: %SW_causa Host ecf4.xxxxx.xxxxx in vlan 501 is flapping between port Po2 and port Gi1/0/43
Dec  6 21:34:21 est: %SW_MATM-4-MACFLAP_NOTIF: Host ecf4.xxxxx.xxxxx in vlan 501 is flapping between port Po2 and port Gi2/0/44
Dec  6 21:34:21 est: %PM-4-ERR_DISABLE: channel-misconfig error detected on Po2, putting Gi1/1/1 in err-disable state
Dec  6 21:34:21 est: %PM-4-ERR_DISABLE: channel-misconfig error detected on Po2, putting Gi1/1/2 in err-disable state
Dec  6 21:34:21 est: %PM-4-ERR_DISABLE: channel-misconfig error detected on Po2, putting Gi2/1/1 in err-disable state
Dec  6 21:34:22 est: %PM-4-ERR_DISABLE: channel-misconfig error detected on Po2, putting Po2 in err-disable state
Dec  6 21:34:22 est: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/1/1, changed state to down
Dec  6 21:34:22 est: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/1/2, changed state to down
Dec  6 21:34:22 est: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/1/1, changed state to down
Dec  6 21:34:22 est: %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel2, changed state to down
Dec  6 21:34:23 est: %LINK-3-UPDOWN: Interface Vlan500, changed state to down
Dec  6 21:34:23 est: %LINK-3-UPDOWN: Interface Vlan501, changed state to down

thanks, P

[MHM Cisco World]

There are two planes 

Control and data 

Control use bpdu to detect loop and discard traffic in one interface if there is loop, 

Data plane forward traffic via any UP interface and it stp is FWD. 

Here I think ISP use filter for bpdu or one site use bpdu filter, this make control plane can not detect loop.

And cause what you see. 

MHM

[paul amaral]

Hi, it has been determined that our ISP actually caused a L2 loop in their network which caused a loop in our shared vlans. I was just trying to figure out is when in err-disable if this is auto recoverable event. 

[balaji.bandi]

My personally suggestion, when the STP Loops or error disable configuring auto-recovery is bad idea.

Instead you can troubleshoot, see where the Loops, make sure you setup and STP priority and Root for the VLAN, so they Block alternative path.

Investigate the MAC (or device) flapping between 2 Port-channel ?

%SW_MATM-4-MACFLAP_NOTIF: Host ecf4.xxxxx.xxxxx in vlan 501 is flapping between port Po2 and port Gi2/0/44

This is indication where to investigate.

%PM-4-ERR_DISABLE: channel-misconfig error detected on Po2, putting Gi1/1/1 in err-disable state

how is your configuration on this port-channel and interface associated with that.

this most likely configuration or STP issue (you need to find out that information)

[paul amaral]

BB, I agree with you that auto recovery for L2 loops is probably bad, but I was wondering if there is a way to do this. From the err-disable command I don't see that as an option in Cisco IOS. I mostly asked because my used was caused by my provider looping their network for a few minutes which caused my port-channel trunks to go into err-disabled. So, I'm wondering if there is a way to auto recover from this. 

[balaji.bandi]

Perosnally auto-recover is bad idea, better also contact provider and check what causing this issue.

[MHM Cisco World · Accepted solution]

The stp effect port-channel 

EtherChannel misconfig guard is enabled

This feature make port go to errdisable 

Channel-misconfig must enable if you want to recovery from this errdisable 

Errdisable recovery cause channel-misconfig

But But 

As @balaji.bandi mention this is not good idea at all.

Errdisable put to protect your SW.

MHM

[paul amaral]

Hi MHM, this is what I wanted to know what err-disable recovery is related to the STP loop issue I have. Although am not going to enable recovery for channel-misconfig I wanted to know what was the related recovery command. Looking back on the log it does state the following on the logs, 

%PM-4-ERR_DISABLE: channel-misconfig error detected 

I just didn't know that channel-misconfig was related to BPDU loop. The channel-misconfig is sort of a vague name, but now I know what is and does. 

thank you.

p 

[MHM Cisco World]

You are so welcome 
MHM