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Third Party VPN Integration

The choice between these three alternatives is based on the balance between costs,** scalability** and management complexity:

Transit Gateway (~$197/month in the described scenario)​

  • Higher fixed cost per attachment.
  • Excellent option for larger topologies, multiple VPCs and scalability with minimal routing complexity.

Site-to-Site VPN + EC2 (~$80/month estimated)​

  • Easy configuration (native AWS solution).
  • Suitable for a moderate number of tunnels, although less flexible than TGW for large topologies.

VPN on EC2 (StrongSwan + Nginx) (~$20–21/month with 1 instance, or ~$40–42/month for HA)​

  • Significantly lower cost.
  • Higher administration and maintenance complexity (instance management, patches, manual failover).
  • Suitable if total traffic is low and if you have staff to operate/monitor the instance.

Transit Gateway​

Acts as a centralized router that allows interconnection between multiple VPCs, on-premises networks and third-party networks.

VPN connections are established through IPsec tunnels, which can be configured to provide high availability and redundancy (two tunnels per VPN connection are generally configured to achieve automatic failover).

vpn

Cost Analysis​

Hypothesis:

  • 3 attachments in the Transit Gateway, corresponding for example to:

    1. VPC (Dev)
    2. VPN (Prod)
    3. VPN (Contingency)

  • 730 hours of monthly usage (24/7).

  • 2 GB monthly transfer per attachment, totaling 6 GB monthly.

  • AWS rates (in most regions):

    • $0.09/hour/attachment.
    • $0.002/GB of data transfer. Costs:

  • Attachment costs: ~$197.10/month

  • Data transfer cost: ~$0.01/month Total sum: ~$197.11/month (rounded to ~$197.22/month in the original example).

Site-to-Site VPN​

A Site-to-Site VPN connection offers two VPN tunnels between a virtual private gateway or transit gateway on the AWS side and a customer gateway on the remote side (on-premise).

Two tunnels for automatic failover or maintenance that AWS usually does that could briefly disable one of the tunnels —> Site-to-Site VPN tunnel endpoint replacement

vpn-2
vpn-3

Cost Analysis​

Hypothesis:

  • 3 connections (VPN) (equivalent to the 3 "attachments" you mentioned: Dev, Main, Contingency).
  • Each VPN is an AWS-managed Site-to-Site tunnel.
  • Site-to-Site VPN cost: $0.05 per hour per VPN
  • 730 hours monthly (24/7).
  • 2 GB monthly transfer per VPN. Costs:
  • VPN (3 connections): ~$109.50
  • Data transfer (6 GB total): ~$0.54
  • Network Load Balancer: ~$20–25 Total sum: ~$130–135 monthly.

VPN on EC2​

In this solution, an EC2 instance is launched on which StrongSwan is installed to establish IPsec tunnels and Nginx as a proxy (normally to route traffic at the application layer towards an Application Load Balancer or other VPC resources).

vpn-4

Cost Analysis​

Hypothesis:

  • 3 tunnels (VPN) configured on the same instance (or on two instances for redundancy).
  • EC2 instance of small size, for example, t3.small (with approx. cost $0.02–0.023/h). Costs:
  • EC2 + EBS: ~$18–20/month (1 instance)
  • Data transfer: ~$0.54/month Total sum: ~$20–21/month (In case of 2 instances for HA => ~$40–42/month.)

Configuration of nginx and ipsec to achieve the connection setup. nginx.conf

load_module /usr/lib/nginx/modules/ngx_stream_module.so;
worker_processes  1;
error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;

events {
    worker_connections  1024;
}

http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';
    access_log  /var/log/nginx/access.log  main;
    sendfile        on;
    keepalive_timeout  65;
    server_tokens off;
}

stream {
    server {
        listen 8180;
        proxy_pass **<URL-ALB>**;
    }
}

iptables.conf

*mangle
:PREROUTING ACCEPT [8165:7991805]
:INPUT ACCEPT [7883:7958068]
:FORWARD ACCEPT [282:33737]
:OUTPUT ACCEPT [5933:572312]
:POSTROUTING ACCEPT [6215:606049]
COMMIT
  *nat
:PREROUTING ACCEPT [159:9540]
:INPUT ACCEPT [159:9540]
:OUTPUT ACCEPT [168:10720]
:POSTROUTING ACCEPT [168:10720]
-A PREROUTING -i eth0 -p tcp -m tcp --dport 2222 -j DNAT --to-destination <IP-BIND>:22
-A PREROUTING -i eth0 -p tcp -m tcp --dport 443 -j DNAT --to-destination <IP-BIND>:443
-A POSTROUTING -p tcp -m tcp --dport 22 -j SNAT --to-source <IP-TUNNEL-BIND>
-A POSTROUTING -p tcp -m tcp --dport 443 -j SNAT --to-source <IP-TUNNEL-BIND>
COMMIT
  *filter
:INPUT ACCEPT [6016:538920]
:FORWARD ACCEPT [123:22565]
:OUTPUT ACCEPT [4614:432344]
-A FORWARD -d <IP-BIND>/32 -p tcp -m tcp --dport 443 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -d <IP-BIND>/32 -p tcp -m tcp --dport 22 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -d <IP-BIND>/32 -p tcp -m tcp --dport 44301 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -d <IP-BIND>/32 -p tcp -m tcp --dport 22 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -d <IP-BIND>/32 -p tcp -m tcp --dport 8180 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
COMMIT