Nagios Support Forum

I have my nagios server inside the firewall. How do I monitor a website as from outside. I can monitor from inside, but I like to monitor the websites from outside. We had a situation that the websites are accessable from inside but not from out side users.Any help please?

That's actually more of a network configuration issue than a Nagios one, but basically what you need to do is allow http traffic on port 80 to be able to get through from the outside. As far as making that happen, you'll have to address that with whoever is in charge of your current firewall.

I could allow the http trafic from the server to port 80 and access out side website. That is not the problem.Our internally hosted websites can be access directely from the nagios server. No need to go ouside the firewall and access it. In reality those web sites are accessable from inside but some times a user from out side cannot. That is want I need to check. The webserver itself is running so there is no problem from inside. But the same web site is not accessable from outside , how do we get alerted. That is the issue.

This is something that's popular, though there is no one solution.

I'd use tor and network anonymity proxy, though the tor network would likely implore you to find another solution unless you were also contributing a great deal. It's been said that since tor is unreliable and slow that it's not a good idea to rely on it for monitoring, I disagree and believe that because it's slow and unreliable that it should therefore be used as a "Can the slow and unreliable internet access my site currently?" measurement. There should be some parent "tor is working AFAICT" host that should cover 90% of the issues/outages you would have with tor itself.

I'd also check to see if your ISP has a proxy server you can use. Ask them if they have one, for lack of a better description, in another state.

I'm sure there are other solutions. If you have another location that you can use as a proxy or if you have web hosting else where then you might try this:

http://http-tunnel.sourceforge.net/
There is a patch floating around that corrects a base64 alignment issue. This project is a php script designed to be used by apache and a perl server, the perl server connects to apache and will pass any network connection(TCP/UDP) you put to it. I've also combined this with openvpn for a seamless way of routing networks together using HTTP.

You'll just need access to some machine outside of your network, whether it be another box of your own running NRPE or an HTTP proxy, and then just route the check command through that.

Seems like a solution, but could you please explain how to route the check command through a machine outside the network

Host withinthesewalls (internal Nagios server):
Full Nagios installation
Service definition with check_command set to check_nrpe, host somewhereovertherainbow, command of check_http_from_outside

Host somewhereovertherainbow (external machine):
Just has the plugins and NRPE
NRPE definition of check_http_from_outside uses check_http plugin, host argument points back at the stuff in your office.

Thus, when Nagios runs the check, it sends it off via check_nrpe to the remote machine, which then processes it into the actual check command, checking the web site from outside, and then returning the result back through NRPE to your internal Nagios server. Make sense?

Where do I insert these check commands?. In the core config manager or during the monitor configuration wizard?

Core Config Manager.