0

So, I have a VPN tunnel configured and working between my SonicWall TZ105 and my AWS VPC. No problems, it works great, as far as it goes.

What I have no clue how to do, is get my EC2 instances inside my VPC, access to the Internet. I want my EC2 instances (which have only a private IP) to be able to route traffic through the SonicWall, and be able to access the internet.

I think I need some combination of routing and NAT policy, to do this?

Can anyone offer me a clue?

Thanks!

1

Although you may or may not be doing all of the things illustrated, your setup is essentially the same as VPC Scenario 3.

In a nutshell...

Create a new VPC route table.

Set its default route (0.0.0.0/0) to point to your Sonicwall, which will have been assigned a virtual private gateway identifier inside VPC -- it looks like vgw-xxxxxxxx.

Associate the subnet(s) where your instances without public IP addresses are located, with this new route table.

You don't need to configure any routing on the AWS side to allow the traffic from the tunnel to reach the instances. This is always possible in VPC -- the VPN is trusted as far as routing is concerned, so routing inbound traffic to the subnets where the instancea are located is implicit.

This will send Internet-bound traffic from the VPC instances out the VPN connection, with their private IP addresses intact. The Sonicwall will need to be configured to do the necessary network address translation on the traffic to allow it to access the Internet using the Sonicwall's public IP address -- which, in the grand scheme, is hopefully the most straightforward part of this setup.

See http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Route_Tables.html

Note that if you -- now, or in the future -- want EC2 instances inside VPC to have AWS-assigned public IP addresses, you will need to place those on different subnets inside VPC. These subnets, known as public subnets, use the VPC's Internet Gateway object (igw-xxxxxxxx) for in and out Internet access.

Note also that if you are using AWS services like DynamoDB, SNS, SQS, etc., you will probably want a NAT instance or NAT gateway in your VPC to allow some level of outbound Internet traffic to short-circuit the path away via your VPN because almost all AWS services, even within the region, require that your instances be able to access "the Internet" in order to get to them. (S3 is one exception, it allows creation of a VPC "endpoint" that obviates the need for Internet access). If you access these services by backhauling over your VPN connection, you will have increased costs and higher latency because you will be paying unnecessarily for the traffic in both directions by routing it outside the AWS region and back again.

Final note, when troubleshooting, you will find that DNS resolution in VPC, by default, always works... even if the rest of your routing is completely and hopelessly wrong... because DNS resolution is handled by some hidden network magic inside VPC. Don't let the fact that DNS is working confuse you. (example: "host x resolves, but I can't actually ping it" -- yes, it almost certainly will always resolve, and that fact doesn't necessarily say anything about your network configuration.)

  • Thanks for the quick reply. I took the steps you outlined, (create VPC routing table, set default route to point to VGW, associate subnets in VPC that only have private IPs, to the new routing table. It's still not working. I suspect an incorrect or missing configuration on the Sonicwall side....more updates as I learn more.... – Mark J. Bobak Aug 4 '16 at 18:11
  • More info: Perhaps the problem still is on the AWS side. When I login to a host in the private Ip only subnet, I can't ping a host in my local office network.....so traffic is not getting to the local network....actually, that also could be a Sonicwall config problem...no good way to definitively determine that. – Mark J. Bobak Aug 4 '16 at 18:14
  • Ok, one more update...Just spent about an hour on the phone w/ Sonicwall support. They had me do a ping of a ublic IP address from a host in the VPC, and they did packet capture, and saw no traffic on Sonicwall originating from VPC. So, apparently, no traffic is reaching the Sonicwall.... – Mark J. Bobak Aug 4 '16 at 19:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.