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Ping with (DUP!) results


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 ?

8 Replies 8

Chad Peterson
Cisco Employee
Cisco Employee

This is tricky to give an exact reason for 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.

Thanks for the explanation ! The wireshark part .. customer aint allowing that to be done :P

Any idea where I can read more on this topic ? Seem like exotic topic.

Thanks !

Are your hosts dual-connected? Do you have asymmetric routing?

Those ESX server generally have more than 1 interface for redundancy purpose.

asymmetric routing - I'm not sure what is this.

If this problem in ESXI VMs then pls do the below

1) Click on the Host (which your VM facing issue) and click configuration tab

2) Click on the Properties of the switch(s)

3) Click on vSwitch  --> Edit  --> Security tab

4) Change : Promiscuous mode : Reject


It works.





Thanks, it worked for me.

1) 2 devices respond to ping.

I've noticed this happening during HSRP Active/Standby state transitions.

Does anybody have an explanation why the HSRP active/standby state transition would cause a duplicate packet?

Every time the state is changed, the end host gets 2 DUP echo reply packets.

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