Troubleshooting Linux Firewalls

This section is nearly identical to the setup of SSH, except that we absolutely, positively want you to stop what you're doing right now and ask yourself, "Why am I using telnet?" It's a very insecure, nonencrypted, trivially sniffable, and/or hijackable protocol. Only use this when SSH isn't available, and even then, be careful when, where, and how you use it.

Telnet uses TCP port 23, so for a shortcut you can just duplicate the SSH rules listed here, replacing references to TCP port 22 to TCP port 23.