The emergence of large-scale quantum computing poses a significant threat to the Public Key Infrastructure (PKI) that secures modern communications. Protocols such as Internet Protocol Security (IPsec), which rely on Internet Key Exchange version 2 (IKEv2) for key establishment, are fundamentally vulnerable to Shor’s algorithm. This vulnerability creates an immediate Har- vest Now, Decrypt Later (HNDL) attack vector, where encrypted data harvested today can be retrospectively decrypted once a sufficiently powerful quantum computer is available. While the National Institute of Standards and Technology (NIST) Post-Quantum Cryptogra- phy (PQC) standardisation process has produced new quantum-resistant algorithms, a simple “rip and replace“ migration strategy is untenable.