IPsecIKEv2

IPsec IKEv2, or IKEv2, is the second version of the Internet Key Exchange protocol used by IPsec to negotiate and manage cryptographic keys and security associations between peers. It facilitates mutual authentication and the selection of cryptographic algorithms for IPsec-protected traffic, enabling secure communication at the IP layer.

IKEv2 distinguishes two types of security associations: the IKE SA, which protects the IKE negotiations themselves, and one or more IPsec CHILD SAs, which protect actual user traffic. The IKEv2 exchange proceeds in two phases: IKE_SA_INIT establishes the IKE SA and cryptographic parameters; IKE_AUTH authenticates the peers and negotiates the first CHILD SAs. Additional CHILD SAs can be created later to handle new traffic or renegotiation.

Key advantages over IKEv1 include a simpler, more efficient handshake, improved resilience to network changes, and streamlined rekeying. IKEv2 supports multiple authentication methods, including pre-shared keys, digital certificates, and EAP. It includes mobility and multihoming support (MOBIKE), NAT traversal capabilities to operate behind Network Address Translation, and robust rekeying mechanisms suitable for VPN and remote-access deployments.

Common deployment scenarios include site-to-site VPNs and remote-access VPNs, where IKEv2 negotiates IPsec ESP or AH parameters for secure data transfer. The protocol is standardized by IETF, with core specifications developing from early IKEv1 definitions to modern IKEv2 standards. In practice, IKEv2 typically uses UDP ports 500 for initial negotiations and 4500 for NAT-T encapsulation, and it supports a wide range of cryptographic suites and authentication methods.

IKEv2 is widely implemented in VPN appliances, operating systems, and security gateways, serving as the primary key exchange mechanism for IPsec in many network environments.