There is an issue I have noticed with VMware systems deployed with Nexus vPC technology that involve traffic only making it out of the vPC by disabling half the vPC or getting rid of the vPC completely. Initially you’re thinking this is a Cisco issue and I am here to tell you that you’re wrong.

In the virtual switch port-groups and the VMNIC teaming there is a load balancing algorithm you can choose from. I have seen issues where the VMNICS are set to route based on IP hash but the port-group could be set to something like route based on originating  port-id. 

If you’re noticing that pinging the machine from the vPC enabled switches, if they have a SVI enabled, that the ping is only responsive on ONE of the devices and from a north end machine, outside the vPC and probably your desk, only gets responses when HALF the vPC is down, you need to immediately check the hashing for the vmnics and the port-group.

Use the command: esxtop – to review what virtual machines are using what vSwitch and vmnic port to further aid in your troubleshooting.

I would highly suggest you keep it the same at both levels, there may be only odd circumstances where mixing these is helpful but you’re likely trading predictability for what may be perceived performance you’re probably not getting.


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