ESX - ACI Problem - Port Down Events

Hello

i have a strange problem. and i really dont know how to go on at this point.

we have 2 DCs both DCs have 2 ESX Servers which are connected to our ACI Streched fabric.

Connection is like:

ESX100 - Leaf 11 port1 & Leaf 12 Port1
ESX101 - Leaf 11 port2 & leaf 12 Port 2

only on leaf 11 i get port down events. onyl for a few seconds down, then it gets up again.

and it just comes and goes.

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we checked the cabling, the sfps -all changed.

still the same.

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on DC2 we also have this problem. so it cant be a HW issue. it has to be something configwise.