IKEv2

IKEv2 (Internet Key Exchange version 2) is a key management protocol used to establish and maintain IPsec security associations. It provides mutual authentication, negotiates cryptographic algorithms, and derives keys for IPsec data traffic. Designed as an improvement over IKEv1, it is more efficient, scalable, and NAT-friendly, and is widely implemented in VPN products and operating systems.

IKEv2 uses a two-phase exchange. The first phase, IKE_SA_INIT, negotiates the IKE Security Association parameters, including Diffie-Hellman groups, encryption and integrity algorithms, and session keys. The second phase, IKE_AUTH, authenticates the peers (via pre-shared keys, certificates, or EAP methods) and establishes one or more IPsec Child SAs that protect traffic through ESP. Additional Child SAs can be created or rekeyed as needed. IKEv2 also supports fast rekeying and mobility across networks, aided by extensions such as MOBIKE and NAT traversal.

Security features include mutual authentication, perfect forward secrecy via Diffie-Hellman, support for multiple authentication methods, NAT traversal, and protection against certain denial-of-service conditions using cookies. The MOBIKE extension provides mobility and multihoming capabilities, allowing IPsec SAs to remain active when devices change networks or IP addresses.

Usage and adoption: IKEv2 is widely supported by vendors and operating systems and is commonly used to establish IPsec VPN tunnels. It is often paired with native IPsec implementations and with EAP-based authentication to provide flexible, secure remote access.

Limitations: successful deployment requires careful configuration of algorithms, DH groups, and authentication methods. While more robust than IKEv1, interoperability can vary across devices, and older hardware may lack full feature support.