We're starting with a running Debian 6.0.3 box fully configured. This particular box is running shorewall in a Three-Interface Firewall configuration. SSH is running on all "networks", and DHCP is running on the local network.

• Install the nagios3 package and all dependencies

$ sudo aptitude install nagios3

_{This will install apache web server using a default config from the upstream packager}

• Modify shorewall (or your firewall implementation accordingly) to allow port 80 traffic.
  • We will modify shorewall rule to utilize the HTTP macro included with shorewall

$ sudo vim /etc/shorewall/rules

#############################################################################################################
#ACTION         SOURCE          DEST            PROTO   DEST    SOURCE          ORIGINAL        RATE            USER/   MARK
#                                                       PORT    PORT(S)         DEST            LIMIT           GROUP
#
#       Accept DNS connections from the firewall to the Internet
#
DNS/ACCEPT      $FW             net
#
#
#       Accept SSH connections from the local network to the firewall and DMZ
#
SSH/ACCEPT      loc             $FW
SSH/ACCEPT      loc             dmz
ACCEPT          net             $FW             tcp     443
ACCEPT          net             loc             tcp     443
#
#       Accept web connections to $FW from net (customized macro.HTTP to include port 8080)
HTTP/ACCEPT     net             $FW
HTTP/ACCEPT     $FW             loc
#
#       DMZ DNS access to the Internet

_{This particular shorewall has been customized to allow port 8080 as well. We will also insure that the firewall can pass traffic to the local network as well. This could be useful if we have situations where a redirect takes place from the external web server to the localhost.}

• Refresh shorewall

$ sudo shorewall refresh

You should now see nagios running at http://domain/nagios3.