[Openswan Users] No response (or no acceptable response) to our first IKE message

[Willie Gillespie]

On 3/19/2012 2:45 PM, Sam wrote:
> Hi,
>
> I have successfully installed Openswan but there seem to an issue with
> the connection to the Cisco VPN or on the network. From the logs am
> seeing something like "*No response (or no acceptable response) to our
> first IKE message*".
>
> Jan 12 04:38:44 localhost pluto[21844]: "VPNCon" #2: initiating Main Mode
> Jan 12 04:51:54 localhost pluto[21844]: "VPNCon" #2: max number of
> retransmissions (20) reached STATE_MAIN_I1.  No response (or no
> acceptable response) to our first IKE message

The first message that is sent out for an IPsec connection is sent to 
UDP port 500.  The other side is not responding to this message at all. 
  Either it is not getting it, or could be ignoring it because of an IKE 
configuration mismatch.  (IKE happens first to exchange keys, Main Mode, 
then it switches to Quick Mode to finish setting up the encrypted tunnel).