Regular Expressions in Nagios

I am a massive fan of Nagios. Whilst it has an initial learning curve it can be an incredibly powerful system. Assuming you have a standardised naming structure for your servers, switches and other infrastructure you can use regular expressions to create a hostgroup that will cover all your devices.

define hostgroup {
    hostgroup_name  Domain Controllers
    alias           All Domain Controllers
    members ^.*dc[0-5]$,^.*(dev|prd|)$
}

If you run a logical structure and have lots of switches or servers this can be a really easy way to ensure you are monitoring all servers or switches and can easily be expanded by simply changing the regex.