10-04-2013 01:30 AM - edited 03-07-2019 03:50 PM
Hello All,
I am new to STP, and i am facing some issues in my network.
I have 2 3750X Switch in Stack,
In logs i am frequently getting MAC Flapping log, while searcing on Internet i am getting only that it's a L2 Loop but no resolution.
Please guide me what should be the Next step for me to resolve the issues asap.
10-04-2013 01:45 AM
can you post the logs :
Host flapping and mac-address flapping can be from server or host end at nic level configuration of teaming (load balancing feature) just check it out the Teaming configuration at server or host level is active/passive and then check the behavior.
or
There could be multiple things that can cause MAC flapping.
Take a look at this paper
Regards
Hope it helps
10-04-2013 02:48 AM
Hello, I have gone through the Document, i think its not issue from any Server Side also we are not using any teaming.
But i have got some output from the Document -
================================================
DC-L3#sh mac address-table dynamic int g1/0/2
Mac Address Table
-------------------------------------------
Vlan Mac Address Type Ports
---- ----------- -------- -----
520 5475.d024.82f7 DYNAMIC Gi1/0/2
520 ec30.91e2.9600 DYNAMIC Gi1/0/2
520 ec30.91e2.dd40 DYNAMIC Gi1/0/2
Total Mac Addresses for this criterion: 3
DC-L3#
DC-L3#sh mac address-table dynamic int g1/0/4
Mac Address Table
-------------------------------------------
Vlan Mac Address Type Ports
---- ----------- -------- -----
820 ec30.91e2.9600 DYNAMIC Gi1/0/4
Total Mac Addresses for this criterion: 1
=============================================================
why the mac address ec30.91e2.9600 is showing on bioth ports.
Logs as Below -
==============================================================
Mar 1 17:05:44.413: %SW_MATM-4-MACFLAP_NOTIF: Host ec30.91e2.9600 in vlan 820
is flapping between port Gi1/0/1 and port Gi1/0/4
*Mar 1 17:05:44.413: %SW_MATM-4-MACFLAP_NOTIF: Host ec30.91e2.9600 in vlan 520
is flapping between port Gi1/0/3 and port Gi1/0/2
=================================================================
10-04-2013 02:57 AM
Can you put the result of these commands:
sh run int gi1/0/2
sh run int gi1/0/4
Regards
10-04-2013 03:05 AM
interface GigabitEthernet1/0/2
switchport access vlan 520
switchport mode access
no keepalive
end
DC-L3#
DC-L3#sh run int g1/0/4
Building configuration...
Current configuration : 128 bytes
!
interface GigabitEthernet1/0/4
switchport access vlan 820
switchport mode access
end
10-04-2013 03:16 AM
Hi;
WHAT is connected on these ports??
I would suggest to configure port security on both ports.
configure terminal
interface interface
switchport port-security
switchport port-security maximum value --> How many mac you want to allow
switchport port-security mac-address mac-address--> you can assign a static mac address to thi port.
or
switchport port-security mac-address sticky
switchport port-security violation shutdown
Regards
HOPE IT HELPS
10-04-2013 03:22 AM
G1/0/1 Towards DC Vlan 820 | G1/0/2 Towards DC Vlan 520 |
G1/0/1 | G1/0/2 |
Vlan 820 | Vlan 520 |
Vlan 520 | Vlan 820 |
G1/0/3 | G1/0/4 |
G1/0/3 Uplink to Port G1/0/4 | G1/0/4 Uplink to Port G1/0/3 |
DC - Datacentre Switches which we dont have sccess
We have made a L2 Loop from Port G1/0/3 to Port G1/0/4, becuase our Switch does not Supports Multicast Routing & we wanted to Forward the Multicast of Vlan 520 to Vlan 820.
Hope you have understand our Scnario
10-04-2013 05:38 AM
Hi Rajput
Error messages are expected as the same mac is being learned from two different ports & in two different VLAS.
Mar 1 17:05:44.413: %SW_MATM-4-MACFLAP_NOTIF: Host ec30.91e2.9600 in vlan 820
is flapping between port Gi1/0/1 and port Gi1/0/4
Suppose switch is learning MAC:ec30.91e2.9600 on VLAN820 on port G1/0/1. By default it propagates that information to all access ports in same VLAN. So this information goes out of port G1/0/4 and reachs the same switch through port G1/0/3 but in different VLAN this time. Hence swith is confused and generating error.
I think till the time your multicast traffic is working properly then you can ignore these errors.
But this is not a good design.
Regards
Bharat
10-04-2013 05:56 AM
Thanks, can understand it's not a good Design. Will try to upgrade the switch but for the meanwhile is there any option to ignore or Block the mac to learn on diffrent ports.
10-04-2013 06:57 AM
Hi Rajput
I have not tried but you can try command suggested by Sandeep to learn static mac from one port.
But if you will do that then you may block traffic on the looped interface. As after being configured for learning single mac it will not be able to learn more mac addresses and will not be able to forward traffic.
It is interesting. I would suggest you to try/test this in lab environment or on standalone switch before implementing to production.
Regards
Bharat
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