In Message Digest 5 (MD5) authentication of BGP4+, you only need to set MD5 authentication passwords for TCP connections, and the authentication is performed by TCP. If the authentication fails, TCP connections cannot be established.
You need to configure Keychain authentication on both BGP4+ peers, and ensure that encryption algorithms and passwords configured for Keychain authentication on both peers are the same. Otherwise, TCP connections cannot be established between BGP4+ peers, and BGP4+ messages cannot be exchanged.