ESXI and flapping between switch ports

Armitage318 used Ask the Experts™

I have an ESXi 5.1 server with just one virtual switch for management network, iSCSI traffic vs storage and VM connectivity.
Both physical NICs of this server  are connected to Cisco switch on access ports.

I noticed on my switch several messages like this:

%SW_MATM-4-MACFLAP_NOTIF: Host xxxx in vlan 100 is flapping between port Gi0/9 and port Gi0/10
%SW_MATM-4-MACFLAP_NOTIF: Host xxxx in vlan 100 is flapping between port Gi0/10 and port Gi0/9

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I checked this URL:

but I am not using neither Etherchannel nor Network failover detection with Beacon probing.
On virtual switch (ESXi) traffic shaping is configured with "Route based on source MAC hash", with both interfaces in Active, so I wouldn't expect flapping since VM's mac address are static.

How can I avoid flapping?
I think I could simply put one network interface in standby mode.. but I'd need to check how much traffic is on that link.
Thank you!
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Create a static trunk (etherchannel) for both physical ports.

If you have two ports, two physical cables, why waste a port in standby.

Have two ports active/active for resilience and throughput.

Here you go have a read of this link

Although very old, still very relevant.


Hi Andrew, thank you.

one doubt: can portgroups override virtual switch configuration?

For example: vSwitch0 has two nic (vmnic0 and vmnic1).

I put vmnic0 "active" and leave vmnic1 in "standby".

Inside this vSwitch, I configure few portgroups.
Can I tell that portgroup "x" should only use vmnic1 and vmnic0 in standby?

Thank you!

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