🌐 Networking

IKE (Internet Key Exchange)

The protocol IPsec uses to negotiate cryptographic parameters, exchange keys, and authenticate peers before a tunnel is established. It listens on UDP/500, and on UDP/4500 when NAT traversal is used, which makes it internet-facing on most VPN gateways.

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How to Lock Down IKE and IPsec Ports to Known VPN Peers

Site-to-site VPN peers have known addresses, yet most firewalls accept IKE from the whole internet. Here is how to replace implied rules with explicit peer allowlists and verify the change.

intermediate 6 min read

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