ufw enable
ufw disable
Enable or disable the firewall.
ufw allow in http
ufw reject telnet comment 'telnet is not encrypted'
Allow all incoming HTTP traffic and reject telnet globally (normally 'deny' is used but 'reject' will explicitly reject a connection).
ufw allow in from 10.254.254.0/24 to any port 22
ufw allow in from 2001:db8::/32 to any port 22
Allow incoming ssh from certain hosts.
ufw limit ssh
Enable rate limiting for ssh, preventing more than 6 access attempts for an IP address for 30 seconds.
ufw allow in http/tcp
ufw allow in http/tcp proto ipv6
Special case for only TCP traffic, or only IPv6.