Cisco interface - Port Flapping

[BrendanMarmont]

Our switch displaying the following when turning on terminal monitor (This is just a few of the offending ports)

46w3d: %C4K_EBM-4-HOSTFLAPPING: Host 00:50:56:98:48:86 in vlan 10 is flapping between port Gi3/8 and port Gi2/26

46w3d: %C4K_EBM-4-HOSTFLAPPING: Host 00:50:56:AB:46:C4 in vlan 10 is flapping between port Gi2/26 and port Gi2/27

46w3d: %C4K_EBM-4-HOSTFLAPPING: Host 00:50:56:98:59:0B in vlan 10 is flapping between port Gi2/23 and port Gi3/34

46w3d: %C4K_EBM-4-HOSTFLAPPING: Host 00:50:56:B6:48:C3 in vlan 10 is flapping between port Gi3/9 and port Gi3/41

46w3d: %C4K_EBM-4-HOSTFLAPPING: Host 00:50:56:B6:2C:06 in vlan 10 is flapping between port Gi3/24 and port Gi2/34

46w3d: %C4K_EBM-4-HOSTFLAPPING: Host 00:50:56:98:7A:22 in vlan 10 is flapping between port Gi3/7 and port Gi3/41

Ports are configured as below and all relate to our VMware host NICs.

interface GigabitEthernet3/7

description VSH02 - Nic 9

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 10-13,30,50

switchport mode trunk

end

Our vSwitch is setup with Link Staus only for failover detection and LB is using Route based on IP hash.

From what I understand this is causing latency on our network and possibly STP issues? Has anyone got a resolution for this?

Thanks

Brendan

[Josh26]

Hi,

Firstly - flapping addresses have nothing to do with STP or latency.

You could however enable "portfast" on the relevant port, for various reasons this will be an improvement to the service.

Flapping is normal, it's part of vmware sending from both NICs. You can advise the switch it is normal by creating an etherchannel. Note ESXi does not support LACP, so you can only run "channel-group 1 mode on".

[BrendanMarmont]

Cheers for that, I put the offending interfaces into 2 port-channel (4 Nics per channel) plus a 3rd channel for v-motion.

Part of my config if it help someone else below...

interface Port-channel2

description VSH03 Etherchannel Group 1

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 10-13,30

switchport mode trunk

switchport nonegotiate

!

interface Port-channel3

description VSH03 Etherchannel Group 2

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 10-13,30

switchport mode trunk

switchport nonegotiate

!

interface Port-channel4

description VSH03 Etherchannel V-Motion

switchport access vlan 50

switchport mode access

interface GigabitEthernet3/19

description VSH03 - Nic 2

switchport access vlan 50

switchport mode access

channel-group 4 mode on

!

interface GigabitEthernet3/18

desc VSH03 - Nic 3

switchport trunk encapsulation dot1q

switchport mode trunk

switchport nonegotiate

channel-group 3 mode on

!

interface GigabitEthernet2/46

desc VSH03 - Nic 4

switchport trunk encapsulation dot1q

switchport mode trunk

switchport nonegotiate

channel-group 2 mode on

[a_p_]

When you use "Route based on IP hash" you have to configure link-aggregation

see:http://www.vmware.com/files/pdf/virtual_networking_concepts.pdf

from the manual:

Route based on IP hash ..... All adapters in the NIC team must be attached to the same physical switch or an appropriate set of stacked physical switches. (Contact your switch vendor to find out whether 802.3ad teaming is supported across multiple stacked chassis.) That switch or set of stacked switches must be 802.3ad-compliant and configured to use that link-aggregation standard in static mode (that is, with no LACP). All adapters must be active. You should make the setting on the virtual switch and ensure that it is inherited by all port groups within that virtual switch

André