Which AES mode should be used in a Cisco SD-WAN environment that includes multicast applications?

Electronic Code Book (ECB) mode is generally insecure for data larger than a single block due to its deterministic nature and lack of integrity protection, making it unsuitable for general data encryption like in SD-WAN.

Cipher Feedback (CFB) mode operates as a stream cipher but is typically slower than GCM and does not inherently provide authentication or integrity by itself, requiring additional mechanisms.

Cipher Block Chaining (CBC) mode is less efficient for parallel processing compared to GCM, and its block chaining nature can complicate key management and synchronization across multiple receivers for multicast scenarios.

Galois/Counter Mode (GCM) is the preferred AES mode for IPsec in Cisco SD-WAN, especially when multicast applications are present, because it offers excellent performance due to parallel processing capabilities and provides both data confidentiality and integrity through authenticated encryption, which is beneficial for multicast traffic.