Then you should be set.

• First install shorewall “$ apt-get intall shorewall”
• Enter /etc/shorewall
• Copy the example files from /usr/share/doc/shorewall-common/default-config/ (might also be located in /usr/share/doc/shorewall/default-config/) “$ cp /usr/share/doc/shorewall-common/default-config/* .”
• Edit the files and enter the data that your system has
  • First create zones “$ nano zones”

     #ZONE   TYPE            OPTIONS         IN OPTIONS                OUT OPTIONS
    fw      firewall
    net     ipv4
    vpn     ipv4

  • Connect zones with interfaces”$ nano interfaces”

     #ZONE   INTERFACE       BROADCAST       OPTIONS
    net     eth0            detect          tcpflags,blacklist,dhcp
    vpn	tun0		-

  • Create policies “$ nano policy”

     #SOURCE         DEST            POLICY          LOG LEVEL       LIMIT:BURST
    fw              net             ACCEPT
    vpn             net             ACCEPT
    vpn             fw              ACCEPT
    fw              vpn             ACCEPT
    net             all             DROP            info
    all             all             DROP            info

  • Create rules “$ nano rules”

     #ACTION SOURCE          DEST            PROTO   DEST    SOURCE          ORIGINAL        RATE            USER/
    #                                               PORT(S) PORT(S)         DEST            LIMIT           GROUP
    ACCEPT          net             fw             tcp     22 # ssh
    ACCEPT          net             fw             tcp     80 # web

  • Verify that the rules are fine “$ shorewall check”
  • Edit /etc/default/shorewall and set startup to 1

     # prevent startup with default configuration
    # set the following varible to 1 in order to allow Shorewall to start
     
    startup=1

  • Start the firewall “$ /etc/init.d/shorewall start”

If you later decide to update rules, zones etc run “$ /etc/init.d/shorewall restart” to load the changes.