Learn how to disable SMB 1 or NetBIOS to prevent failover.
This article is intended for enterprise and education system administrators.
SMB 1 and NetBIOS are enabled by default in macOS to improve compatibility with third-party products. macOS will attempt to use the later versions of SMB, as well as DNS and port 445, with failover to port 139 and SMB 1 as needed. You can disable SMB 1 or NetBIOS to prevent this failover.
To disable SMB 1, add the following line to the /etc/nsmb.conf file:
protocol_vers_map=6
To disable NetBIOS, add the following line to the /etc/nsmb.conf file:
port445=no_netbios
The /etc/nsmb.conf file doesn’t exist by default. To create one and apply both of the above changes, use the following Terminal commands:
echo “[default]” | sudo tee -a /etc/nsmb.conf
echo “protocol_vers_map=6” | sudo tee -a /etc/nsmb.conf
echo “port445=no_netbios” | sudo tee -a /etc/nsmb.conf
To revert the above changes, you can delete the /etc/nsmb.conf file safely.
Published Date: December 14, 2020 | https://support.apple.com/en-us/HT211927
