Port 4500: IPsec NAT-T
Port 4500 carries IPsec traffic once IKE on port 500 detects that a NAT device sits between the two VPN endpoints. Wrapping the IPsec packets in UDP on this port lets them pass through routers that would otherwise break the tunnel.
| Port number | 4500 |
|---|---|
| Service | IPsec NAT Traversal |
| Protocol | UDP |
| Category | Routing |
| Default encryption | No |
Frequently asked questions
What is port 4500 used for?
Port 4500 carries IPsec traffic once IKE on port 500 detects that a NAT device sits between the two VPN endpoints. Wrapping the IPsec packets in UDP on this port lets them pass through routers that would otherwise break the tunnel.
Is port 4500 TCP or UDP?
Port 4500 (IPsec NAT-T) uses UDP.
Is port 4500 secure?
Port 4500 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 4500 on my firewall?
Only if you specifically need IPsec NAT-T. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.