Firewall

- open firewall
$ iptables -F

- hosts.allow, hosts.deny
/etc/hosts.deny
#+TITLE: hosts.deny
#+begin_src
...
ALL : ALL
#+end_src

#+TITLE: hosts.allow
#+begin_src
..
in.telnetd : 10.10.30.0/255.255.255.0
..
#+end_src