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Duplicate first packet detected!

Cisco VPN 3015 running 3.6.5.Rel.

3.6.2B Clients connecting with preshared key config.

I get this working from many locations except one. Remote location continually gets Duplicate first packet detected! in the 3015 logs. After numerous tries the client will eventually connect.

I have tried using UDP 10000 no encapsulation and Transparent tunnelling using IPSEC over udp/tcp -- no improvements.

The ISP claims they have set up a traditional NAT 1 to 1 internal IP address to an external address with all ports open.

No firewall on their, just a router apparently.

Like I said I can connect to the Internet and use all of their account info. and make a connection no problem.



Re: Duplicate first packet detected!

The message indicates that the concentrator is receiving the initial message from the client twice. This might be seen when the concentrators reply does not get back to the client and the client sends out another message. The fact that all your other clients are working just fine with the same COncentrator indicates that the problem could be with the provide or the specific PC itself. The best solution would be to take another PC to the problamatic clients end and try establising the connection. If you can connect fine, the problem is be with the PC itself. Else, something might be going wrong on your provider's end.

Community Member

Re: Duplicate first packet detected!

Thanks for the reply. I am suspecting the ISP totally. We have created a true NAT 1-to-1 Internal IP to External IP address at the ISP and this seems to have resolved the problem somewhat. End user still has difficulty connecting on a consistent basis. I am thinking the routing is flawed somewhere.


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