Diameter Redirect Between Client and Server

A technique redirects a Diameter client command from a first server that has become unavailable to a second server consistent with a Diameter protocol. A method includes identifying a first authentication server as unavailable based on a redirect indication received from a second authentication server via a routing agent in response to a request for authentication of a user to the first authentication server. The method includes authenticating the user by the second authentication server in response to a subsequent request for authentication of the user to the second authentication server. The subsequent request for authentication includes an indication of a failure of the first authentication server. The method may include establishing a first service session in response to authenticating the user by the first authentication server and maintaining the first service session using the IP address of the first service session while the second authentication server authenticates the user.