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New Member

HOSTFLAPPING

Can anyone help me with this log, i think is a problem with spannig-tree but can anyone help me where the problem with comes from.

Nov 16 13:10:12: %C4K_EBM-4-HOSTFLAPPING: Host 02:02:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Gi7/19

Nov 16 13:10:26: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Po1

Nov 16 13:10:42: %C4K_EBM-4-HOSTFLAPPING: Host 02:02:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Gi7/19

14 REPLIES
Hall of Fame Super Bronze

Re: HOSTFLAPPING

Identify what you have connected on port 6/17 and 7/19. The switch thinks it's the same device because both ports are learning the same MAC Address (02:02:0A:00:07:93).

If it's the same device and it's configured for load balancing, you must configure load balancing at the switch as well.

Same goes for port 6/17 and Port-Channel1.

New Member

Re: HOSTFLAPPING

The deviceon the port 6/17 is a cisco 7204r and the other device is a cluster.

Silver

Re: HOSTFLAPPING

Hi ,

You can use the command show mac-address-table on switch to see mac address of ports.

The %C4K_EBM-4-HOSTFLAPPING:Host [mac-addr] in vlan [dec] is flapping between port [char] and port [char] error message signifies that the specified host is detected as a source address on multiple ports. Typically, a host is supposed to be learned on only one port.

These are common causes for this error message:

There is an spanning-tree loop.

All traffic from the specified host is temporarily dropped. After 15 seconds, forwarding is re-enabled. If the problem persists, the traffic from the problem host is dropped indefinitely. (However, in this case, expect the switch to see a few more MAC addresses on different VLANs.)

The host is connected to ports x/y, and x/y runs a type of clustering or redundancy and has an issue with this mechanism.

If the MAC address specified in the error message can be traced, this is likely the issue. For an example, refer to this error message:

%C4K_EBM-4-HOSTFLAPPING: Host 02:01:00:00:00:00 in vlan x is flapping between port Gi x/y and port Gi x/y

The MAC address 02:01:00:00:00:00 appears to be associated to Microsoft's Network Load Balancing (NLB) Service Heartbeat. It is suggested that the connected device (Microsoft host) be checked for causing these messages.

To resolve this problem, make sure that spanning tree is enabled. This prevents spanning tree loops. If spanning tree is disabled, make sure there are no spanning tree loops in the network.

To display spanning-tree state information for the VLAN ID mentioned in the error message, issue the show spanning-tree vlan vlan_id detail command and look for the last topology change.

If the MAC address in the error message is related to Microsoft Network Load Balancing (NLB), then you need to disable or clear the Network Load Balancing check box.

To disable NLB perform the procedure in Disabling Network Load Balancing (NLB).

Thanks,

satish

Re: HOSTFLAPPING

Are the ports in question connected to Wireless Access points? If it is, the user may be trying to connect to the network through different APs and from the switch perspective the host appears to be flapping between those ports.

HTH

Sundar

New Member

Re: HOSTFLAPPING

no, they are cluster and a router.

New Member

Re: HOSTFLAPPING

this is in one 4507r

Nov 16 11:38:55: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:07:93 in vlan 4 is fl

apping between port Po1 and port Gi7/19

Nov 16 11:39:25: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:07:93 in vlan 4 is fl

apping between port Po1 and port Gi7/19

Nov 16 11:39:56: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:07:93 in vlan 4 is fl

apping between port Po1 and port Gi7/19

Nov 16 11:40:26: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:07:93 in vlan 4 is fl

apping between port Po1 and port Gi7/19

Nov 16 11:40:56: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:07:93 in vlan 4 is fl

apping between port Po1 and port Gi7/19

Nov 16 11:41:25: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:07:93 in vlan 4 is fl

apping between port Po1 and port Gi7/19

Nov 16 11:41:56: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:07:93 in vlan 4 is fl

apping between port Po1 and port Gi7/19

Nov 16 11:42:25: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:07:93 in vlan 4 is fl

apping between port Po1 and port Gi7/19

Nov 16 11:42:56: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:07:93 in vlan 4 is fl

apping between port Po1 and port Gi7/19

and this is in another:

apping between port Gi6/17 and port Gi7/19

Nov 16 18:24:43: %C4K_EBM-4-HOSTFLAPPING: Host 02:02:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Gi7/19

Nov 16 18:25:13: %C4K_EBM-4-HOSTFLAPPING: Host 02:02:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Gi7/19

Nov 16 18:25:42: %C4K_EBM-4-HOSTFLAPPING: Host 00:11:43:12:AF:0B in vlan 4 is fl

apping between port Gi6/17 and port Gi4/1

Nov 16 18:25:43: %C4K_EBM-4-HOSTFLAPPING: Host 02:02:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Gi7/19

Nov 16 18:26:13: %C4K_EBM-4-HOSTFLAPPING: Host 02:02:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Gi7/19

Nov 16 18:26:27: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Po1

Nov 16 18:26:43: %C4K_EBM-4-HOSTFLAPPING: Host 02:02:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Gi7/19

Nov 16 18:27:13: %C4K_EBM-4-HOSTFLAPPING: Host 02:02:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Gi7/19

Nov 16 18:27:43: %C4K_EBM-4-HOSTFLAPPING: Host 02:02:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Gi7/19

Nov 16 18:28:13: %C4K_EBM-4-HOSTFLAPPING: Host 02:02:0A:00:07:93 in vlan 4 is fl

apping between port Gi6/17 and port Gi7/19

both works as hsrp

Silver

Re: HOSTFLAPPING

Hi ,

Is it possible to disconnect and connect cable connecting to port G7/19.

Thanks,

satish

Re: HOSTFLAPPING

Are you doing bridging on the 7204r? i.e, is the interface to 4507 on the 7204r router configured with the bridge-group (#) command?

New Member

Re: HOSTFLAPPING

7204

interface FastEthernet0/0

ip address 10.0.4.39 255.255.252.0

duplex full

bridge-group 1

4507r

interface GigabitEthernet6/17

description Cisco7204vxr

switchport access vlan 4

switchport mode access

logging event link-status

speed 100

duplex full

spanning-tree portfast

spanning-tree bpdufilter enable

spanning-tree bpduguard enable

Re: HOSTFLAPPING

Do you have spanning tree enabled on the 7204 or post the output of show spanning-tree 1. Also, post the output of show spanning-tree vlan 4 from the master switch of the cluster.

New Member

Re: HOSTFLAPPING

i atach a file.

New Member

Re: HOSTFLAPPING

this is a cluster that i can not disconect.

New Member

Re: HOSTFLAPPING

Hey buddies,

Has anybody found a solution for this issue?

Ricardo ... have you found a solution?

I have exactly the same problem: same syslog messages and the both cores go down ... we have to reboot both cores in order to restablish the services.

It is very difficult to track the source of the problem.

Maybe this link could help many of you to make the tracking of a forwarding loop:

http://www.cisco.com/en/US/partner/tech/tk389/tk621/technologies_tech_note09186a0080136673.shtml

I am beginning to thinks that is a bug in IOS

:(

Regards

Pedro

New Member

Re: HOSTFLAPPING

hi Pedro

not, yet.

Aun tengo el problema desde ese tiempo para aca creo haber dado con una posible causa, el problema viene de servidores que utilizan NLB de Microsoft, por lo que he averiguado Microsoft recomienda no utlizar esta configuracion con equipos cisco, y por una pregunta que coloque en este forum cisco no tiene una solucion para ello. Indicame por favor si tus servidores utilizan tambien NLB.

Salduos

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