I receive replies with (DUP!) errors. I read that it due to two device replies to the same ping request.
I can't seem to find further details on the subject. I trace the IP in question and it was drilled down to 2 switches with ESX server behind the ports.
The 2 switch is connect to a core switch. How do I resolve this issues ?
This is tricky to give an exact reason for this...here are some possibilities:
1) 2 devices respond to ping.
2) Echo requests are getting duplicated in network and end host is responding to each.
3) End device receives correct echo request, and the response is getting duplicated somewhere in the network.
To track this down, use Wireshark to sniff the packets first at the client generating the pings. This will first show you if it is multiple machines responding.
Next sniff on the host you are pinging. See if he receives multiple echo requests.
That will give you a good start about where to look, and why this is happening.