AWS Lab · Interactiveplay · 5–10 min

VPN Simulator: Break It Safely

Before you spend a cent in a real account, get the tunnel UP here. Make the real choices, make the real mistakes, and see exactly why AWS would fail, instantly.

From your mentor

This is the part that builds confidence: failing safely. Toggle the wrong choices on purpose, read the diagnosis, then fix them one by one until the packet crosses. When it clicks here, the real lab feels easy.

01

Get the tunnel up

Flip each setting between the right choice and the common mistake. The tunnel state, the ping, and the diagnosis update live, just like the real thing.

Your configuration

Customer Gateway IP

strongSwan security group

Pre-shared key

Route propagation (cloud route table)

Tunnel can be UP, but without route propagation the cloud subnet has no route back, replies never return.

On-prem route + source/dest check

Tunnel

UP

Ping across

timeout

On-prem host

strongSwan

Internet

AWS VGW

EC2

✕
traffic is encrypted between strongSwan and the AWS VGW

Tunnel UP, but the ping fails

Tunnel is UP, but the cloud subnet has no route back. Enable route propagation on the cloud route table.

?

Worth pondering

Notice it starts with route propagation off, on purpose. That’s the #1 real-world trap: the tunnel goes UP, everything looks fine, and the ping still times out. Experience that here once and you’ll never be fooled by it in production.
02

What you’re actually learning

Every toggle maps to a real decision in the working VPN lab. The simulator enforces the same dependency chain AWS does: IKE must reach the peer and authenticate before the tunnel comes UP, and routes must exist on both sides before a packet returns.

The order failures happen in

Reachability → ports → authentication bring the tunnel up. Route propagation and the on-prem route make the ping succeed. A green tunnel with a failing ping is almost always a routing problem, never an IKE one, the simulator drills that distinction into you.

Next up

Now do it for real → Lab: Your First Working Site-to-Site VPN

Same choices, real AWS account. You’ve already seen every failure mode here, so you’ll recognise and fix them instantly.