If you are not familar with firewalld and the firewall-cmd, check out our Getting Started article.

The --add-port=port_number/protocol option can be used to allow connections to a protocol.

firewall-cmd --add-protocol=smb2 --permanent
firewall-cmd --reload

Or --remove-port=port_number/protocol to remove a protocol

firewall-cmd --remove-protocol=smb --permanent
firewall-cmd --reload

The --check-config command can be used to ensure there are no configuration errors.

~]$ firewall-cmd --check-config
success

firewall-cmd --list-all will show the allowed protocol.

~]# firewall-cmd --list-all
public
  target: default
  icmp-block-inversion: no
  interfaces: eth0
  sources:
  services:
  ports:
  protocols: smb2
  masquerade: no
  forward-ports:
  sourceports:
  icmp-blocks:
  rich rules: