! interface FastEthernet0/1 description PC terminal switchport access vlan 991 switchport mode access no snmp trap link-status no mdix auto end
Rapid spanning-tree is enabled on all switches. There are no loops (the 2960 switches are connected with only 1 uplink to the 4503) anywhere.
now my problem. The terminals connected to the 2960 switches are turned on every morning. Some terminals won't show the startup screen (no connection) but when you refresh, the connection is fine. The log of the 2960's show the following on april 7:
Apr 7 09:00:04.360 GMT+1: %SW_MATM-4-MACFLAP_NOTIF: Host 00e0.c549.0446 in vlan 991 is flapping between port Gi0/1 and port Fa0/5 Apr 7 09:00:04.628 GMT+1: %SW_MATM-4-MACFLAP_NOTIF: Host 00e0.c549.038b in vlan 991 is flapping between port Gi0/1 and port Fa0/1
Apr 7 09:00:09.871 GMT+1: %C4K_EBM-4-HOSTFLAPPING: Host 00:E0:C5:49:04:46 in vlan 991 is flapping between port Fa3/46 and port Fa3/47 Apr 7 09:00:11.027 GMT+1: %C4K_EBM-4-HOSTFLAPPING: Host 00:E0:C5:49:03:8B in vlan 991 is flapping between port Fa3/46 and port Fa3/47
-------- April 8--------
Apr 8 09:02:39.168 GMT+1: %SW_MATM-4-MACFLAP_NOTIF: Host 00e0.c549.0431 in vlan 991 is flapping between port Gi0/1 and port Fa0/5
Apr 8 09:02:39.445 GMT+1: %LINK-3-UPDOWN: Interface FastEthernet0/2, changed state to down Apr 8 09:02:42.465 GMT+1: %SW_MATM-4-MACFLAP_NOTIF: Host 00e0.c549.0431 in vlan 991 is flapping between port Fa0/5 and port Gi0/1 Apr 8 09:02:42.926 GMT+1: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down Apr 8 09:02:43.530 GMT+1: %LINK-3-UPDOWN: Interface FastEthernet0/2, changed state to up
MAC 00e0.c549.0446 is physically connected to 2960 switch2, Fa 0/5 and the MAC address table on 2960 Switch 1 shows the address on Gi 0/1 (which is correct).
So, can someone explain to me why I see these flapping messages wihtout loops of etherchannels or whatsoever? Just simple access ports over single trunks?
The problem of Mac flapping between the ports in switches can be due to network switches for misconfigurations that might cause a data-forwarding loop
- It could be a wrong setup - It could be resolved by disabling unused NIC cards in the servers connected to the switch could fix the problem of MAC address Flapping. - It could resolve by bad Hardware replacement(switch).
and more specifically check the e server providers to see if the OS and server platform support 'NIC' Teaming (NIC Bonding).
FYI - NIC teaming allows users to group two or more physical NICs into a single logical network device called a bond. Once a logical NIC is configured, the virtual machine is not aware of the underlying physical NICs. Packets sent to the logical NIC are dispatched to one of the physical NICs in the bond and packets arriving at any of the physical NICs are automatically directed to the appropriate logical NIC.
If one of the underlying physical NICs is broken or its cable has been unplugged, server will detect the fault condition and automatically move traffic to another NIC in the bond. This capability eliminates a single point of failure for any one physical NIC and makes the overall network connection fault-tolerant.
The thing is: there are no loops in that part of the network. It's just a couple of cascaded switches. The last switch has the two smaller 2960 PoE powered switches attached to them. Attached to those switches are the client PC's. All those PC's are connected with only one NIC to one of the small switches.
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