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New Member

VPN - Duplicate IP packet detected error

When one of my users connected through VPN client connect into our VPN concentrator (3005), I see on my log file "Duplicate IP Packet Detected" . This is happening to only this user and user gets an error "remote peer no longer responding.. ".

He is trying to connect from XP machine using cable modem and Netsys for wireless access.

Any insight to this problem is appreciated.

New Member

Re: VPN - Duplicate IP packet detected error

the client is not recieving and processing the return packet from the concentrator

the client sends out it's initial Phase 1 first packet to the concentrator

the concentrator recieves and processes it and sends a response to the client

after the concentrator does this it waits for the next packets from the client.


the client will attempt to send out the first Phase 1 packet

if it does not recieve a responce from the Concentrator it will try 2 more times

if the client does not get a response after those 3 times, the client in gets the "remote peer no responding" error

Enabling logging on the client will verify this

what is happening to you is that the concentrator has already seen and processed the that first packet but the client is not recieving it.

hince the "dup 1st packet" in Concentrator Event Log


"Remote peer no longer responding" on the client

the path:

Client to Concentrator is good


Concentrator to Client is not because it is not recieving in order to process the response from the concentrator

you can try rebooting the client device but, i would check the documentation of the cable modem and wireless devices to make sure they have no issues with IKE

New Member

Re: VPN - Duplicate IP packet detected error


I´ve ran in to the same(or similar) problem and have come to the conclusion that the problem lies in the DSL/Cable router through which the user lights up the VPN Client.

Depending on the routers capabilities of handling NAT with IPSec traffic, the user may experience this problem if he/she tries to initiate VPN sessions from more than one computer.

The solution would be to invest in a more powerful router, or if possible always run the VPN client on the same computer.



New Member

Re: VPN - Duplicate IP packet detected error

For whatever it's worth, I had this exact same issue with a user, and I sent them the latest VPN Client and that fixed it.