SMB Protocol Negotiation Failed #

Normally SMB takes care of choosing the appropriate protocol for each connection. However, if the offered protocols are out of client’s default range, it will return an error message like this:

Protocol negotiation failed: NT_STATUS_IO_TIMEOUT

Solution #

Edit the connection protocol range in the client configuration file.
Add client min protocol and client max protocol settings to /etc/samba/smb.conf under [global].

# /etc/samba/smb.conf
[global]
client min protocol = CORE
client max protocol = SMB3