IKEv2IPsec

IKEv2/IPsec is a widely used standard for securing virtual private network (VPN) connections. It combines the Internet Key Exchange version 2 (IKEv2) protocol, which manages security associations and key exchange, with the IPsec protocol suite that protects IP packets through encryption, integrity, and authentication.

IKEv2 handles mutual authentication and the negotiation of cryptographic algorithms and keys. It creates an IKE_SA to protect subsequent negotiations and then one or more CHILD_SAs that actually protect the IP traffic. It supports various authentication methods, including pre-shared keys (PSK), X.509 certificates, and Extensible Authentication Protocol (EAP) methods such as EAP-TLS. It also supports Mobility and Multihoming (MOBIKE) for roaming devices and NAT traversal (NAT-T) when devices are behind NAT.

IPsec provides the data security layer, typically using the Encapsulating Security Payload (ESP) protocol to offer encryption and integrity, though Authentication Header (AH) exists for integrity-only protection. IKEv2 negotiates the IPsec SA parameters, such as encryption and integrity algorithms and the Diffie-Hellman group for forward secrecy. The IKEv2 and IPsec layers can be rekeyed independently, with IKEv2 refreshing SAs and IPsec refreshing data SAs as needed.

Ports and transport: IKEv2 normally uses UDP port 500; NAT-T uses UDP port 4500. The standard is defined in RFC 7296 and enjoys broad support across major operating systems and devices, including Windows, macOS, Linux, iOS, and Android, contributing to its popularity for remote-access VPNs.

Security considerations include using strong authentication, proper certificate management or secure PSKs, and up-to-date cryptographic suites. Misconfigurations can weaken security or disrupt connectivity, so careful configuration and monitoring are advised.