Private Subnets and VPN Tunnels in AWS
VPN Tunnel
The idea is for all your private subnets to route via the VPN Tunnel. Create a custom route table shown below for the first private subnet. This is the same routing table you will attach to successive subnets. A SINGLE routing table can have multiple routes
Testing the VPN Tunnel
| Protocol type | Protocol number | ICMP type | ICMP code | Source IP |
|---|---|---|---|---|
| ICMP | 1 | 8 (Echo Request) | N/A | The public IPv4 address of your on premises computer or cidr range |
- Spin up an Ec2 instance, associate it with a SG that allows PING traffic (ICMP). Now, get its private IP address (for example,
10.0.0.4). The Amazon EC2 console displays the address as part of the instance’s details. - From a computer in your network that is behind the customer gateway device, use the
pingcommand with the instance’s private IP address. A successful response is similar to the following:ping10.0.0.4
PRIVATE Subnets need a route to both the Internet (Nat gateway) and to the VPN Tunnel (VgW). How do you provide both in one custom route table?
The ‘destination’ fields are different.
- For Private Subnets getting to On PRem Addresses – the destination is anything in the VPC (entire CIDR block – 10.0.0.0/16) and target is VgW
- For Private Subnets getting to Internet, the destination is 0.0.0.0/0 and the target is the NAT GW
Anuj holds professional certifications in Google Cloud, AWS as well as certifications in Docker and App Performance Tools such as New Relic. He specializes in Cloud Security, Data Encryption and Container Technologies.
Anuj Varma – who has written 1210 posts on Anuj Varma, Hands-On Technology Architect, Clean Air Activist.
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