Port 500: ISAKMP/IKE
Port 500 is used by IKE, the Internet Key Exchange protocol that negotiates and manages the security keys for an IPsec VPN tunnel. NAT traversal for the same negotiation falls back to port 4500.
UDPRoutingUnencrypted by defaultIANA assigned
| Port number | 500 |
|---|---|
| Service | Internet Key Exchange (IPsec) |
| Protocol | UDP |
| Category | Routing |
| Default encryption | No |
Security note. Port 500 is not encrypted by default. Restrict it to trusted networks, or use an encrypted alternative where one exists, to avoid exposing credentials and data in transit.
Frequently asked questions
What is port 500 used for?
Port 500 is used by IKE, the Internet Key Exchange protocol that negotiates and manages the security keys for an IPsec VPN tunnel. NAT traversal for the same negotiation falls back to port 4500.
Is port 500 TCP or UDP?
Port 500 (ISAKMP/IKE) uses UDP.
Is port 500 secure?
Port 500 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 500 on my firewall?
Only if you specifically need ISAKMP/IKE. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.