500 ISAKMP / IKEInternet Key Exchange for IPsec VPN tunnel negotiation.
Site-to-site and remote-access IPsec VPNs. Pair with UDP/4500 for NAT-T.
| Transport | Status | Meaning |
|---|---|---|
| TCP | Assigned | Assigned by IANA, but not standardized, specified, or widely used on this port. |
| UDP | Yes | Assigned by IANA and standardized, specified, or widely used on this port. |
| SCTP | — | Not applicable for this transport. |
| DCCP | — | Not applicable for this transport. |
Well-known (0–1023). System port for a core service. On Unix-like systems, binding it requires superuser privileges.
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