The strongest password authentication for local router access would be one that uses a strong encryption algorithm to hash the password. In Cisco routers, this can be achieved by using the "username [username] secret" command followed by a complex password string which is then encrypted using a strong hashing algorithm like SHA-256 or MD5. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) v1.1 Reference: https://community.cisco.com/t5/networking-documents/understanding-the-differences-between-the-c