I build my own NAT instances from Debian Trixie with Packer on AWS. AWS built-in NAT Gateways use an absurdly outdated and end-of-life version of Amazon Linux and are ridiculously expensive (especially traffic).
The bash configuration is literally a few lines:
cat <<'EOF' | sudo tee /etc/sysctl.d/99-ip-forwarding.conf > /dev/null
net.ipv4.ip_forward=1
EOF
sudo sysctl --system
sudo iptables -t nat -A POSTROUTING -o ens5 -j MASQUERADE
sudo iptables -F FORWARD
sudo iptables -A FORWARD -i ens5 -m state --state RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -o ens5 -j ACCEPT
sudo iptables-save | sudo tee /etc/iptables/rules.v4 > /dev/null
Change ens5 with your instance network interface name. Also, VERY IMPORTANT you must set source_dest_check = false on the EC2 NAT instances.
Also, don’t assign a EIP to your EC2 NAT instances (unless you absolutely must persist a given public IP) as that counterintuitively routes through public traffic. Just use a auto-assigned public IP (no EIP).
NAT instance with EIP
- AWS routes it through the public AWS network infrastructure (hairpinning).
- You get charged $0.01/GB regional data transfer, even if in the same AZ.
The bash configuration is literally a few lines:
Change ens5 with your instance network interface name. Also, VERY IMPORTANT you must set source_dest_check = false on the EC2 NAT instances.Also, don’t assign a EIP to your EC2 NAT instances (unless you absolutely must persist a given public IP) as that counterintuitively routes through public traffic. Just use a auto-assigned public IP (no EIP).