Slash EC2 Outbound Costs: Smart Alternatives to AWS NAT Gateways

Providing outbound internet connectivity to EC2 instances residing in private subnets is a common requirement, but the associated costs, particularly with AWS NAT Gateways, can be a significant concern. This discussion explored various strategies to mitigate these expenses while maintaining necessary functionality.

The Challenge: Expensive NAT Gateways

The original poster highlighted the steep cost of AWS NAT Gateways, at approximately $32 per month per Availability Zone (AZ), before even factoring in data transfer charges. While self-managed NAT instances on small EC2 instances (like t5g.small) offer a cheaper alternative (around $8/month plus EBS), they come with the overhead of setup, maintenance, and ensuring high availability. Users also noted that AWS's official NAT instance AMI is outdated, running on the end-of-life Amazon Linux 1.

Popular Alternative: `fck-nat.dev`

A prominent recommendation was fck-nat.dev, a community-driven solution designed as a cost-effective replacement for AWS NAT Gateways. Key benefits shared by users include:

Significant Cost Savings: It can run on inexpensive EC2 instances.
High Availability: Can be configured within an Auto Scaling Group (ASG) to automatically recover from instance failures.
Dual Functionality: The instance running fck-nat.dev can also serve as a bastion host, further consolidating resources and reducing costs.

This solution directly addresses the maintenance concerns of self-managed NAT instances by providing a ready-to-deploy, community-supported alternative.

Other Cost-Saving Tactics

Centralized NAT: One user suggested routing traffic from instances in multiple AZs through a single NAT Gateway or NAT instance. While this reduces the per-AZ cost, it creates a single point of failure and makes the architecture less resilient to AZ outages. This is a trade-off between cost and availability.
Complex External Routing: A more involved, and perhaps less practical, idea mentioned was using a site-to-site VPN to route traffic through an external server or firewall acting as the NAT device.

The Ideal Long-Term Solution: IPv6

For a more modern and potentially cost-free (for NAT charges) approach to outbound connectivity, deploying services in an IPv6-enabled subnet with an egress-only internet gateway was proposed. Egress-only internet gateways allow outbound communication from instances over IPv6 while preventing unsolicited inbound connections, effectively fulfilling the role of NAT for outbound traffic without the associated NAT gateway charges.

Conclusion