title: Site to Site VPN connection between TMG and AWS keeps dropping
body: <p>AWS VPC &lt;==> TMG</p>
  
  <p>I have an amazon VPC with a VPN IPsec VPN connection connected to a Microsoft Forefront TMG server as a customer gateway hosted on Server 2008 r2 SP1, the TMG application is also patched upto SP2 build 7.0.9193.500. The VPN tunnel will connect, stay connected for a short amount of time (roughly 5-10 minutes) then drop, it will connect and drop, connect and drop. I have ran a ping trace from a workstation on my LAN to the VPC and you can see very clearly the connection going up and down, however the AWS management consoles status is connected. I have no idea why and there aren't any logs in the server event viewer to shine any light on the issue.</p>
  
  <p>I have also set the MTU to 1436 on the external network interface of the TMG box as recomended by Amazon as of this guide:</p>
  
  <p><a href="http://awsdocs.s3.amazonaws.com/VPC/latest/vpc-nag.pdf" rel="nofollow">http://awsdocs.s3.amazonaws.com/VPC/latest/vpc-nag.pdf</a></p>
  
  <p>Does anyone have any suggestion on what I could try to bring some stability to my VPN connection as its practically unusable at the moment.</p>
  
  <p>Many thanks,
  Jon</p>