MAC flapping between ports

[Mubeen]

Hi,

I have 2 ISP's. Cisco 3825 router and Cisco cat 3750. Vlans in the network are: 100, 200, 300

I terminated both ISP's in switch assigning vlan 100 (port 3 of 3750) and vlan 200 (port 4 of 3750). Then I made trunk (vlan 100, 200 on port 2 of 3750) and connected it with router port 0/0.0 and  0/0.1. Router 0/1 is access port coming back to cat 3750 port 1 with vlan 300. and vlan 300 is providing internet to all access switches.

The issue I'm having is MAC address flapping between port 1 and port 6 of cat 3750. whereas port 6 is uplink to access switch. Port 6 is going to error disable state if link flaps a few times

SW_MATM-4-MACFLAP_NOTIF: Host 001c.f6fa.24c1 in vlan 300 is flapping between port Gi1/0/6 and port Gi1/0/1

Have attached router and switch configuration.

[Dennis Mink]

Can you identify what that mac address belongs to?

[Mubeen]

MAC address belongs to port 0/0 of router

[balaji.bandi]

high level couple of my observations :

On Switch :

interface GigabitEthernet1/0/1
switchport access vlan 300
switchport trunk encapsulation dot1q    <-- why you need trunk here ? remove this
switchport mode access 
spanning-tree portfast

Router  :

interface GigabitEthernet0/1   <--- since you connected to above port required access port only not trounk  
description CONNECTION_TO_INTERNAL_NETWORK
ip address 192.168.111.1 255.255.255.0

[Mubeen]

Tried this, still same issue.

[paul driver]

Hello

Sh int trunk <-- both core and access switch
Sh spanning-tree blockedports <-- both core and access switch
Are you running wifi on this network?
Whats the config of the access switch?