Nagios Support Forum

Hello Everyone,

I am new to Nagios and I just wanted to ask if we can use Nagios Core to monitor external or remote machines (both Windows and Linux) and network devices from an internal server. It seems that we can use NSCA for remote Linux machines, but how can we do the same for Windows and remote network devices? So we basically, we need to monitor remote servers and network devices from external domains. How can we achieve this using Nagios Core?

Thanks in advanced,

Arnel

Network devices can be monitored by active or passive checks.

Active checks require a server on the same node/subnet, and would act as a proxy for the active checks (using nrpe from the nagios server to the proxy where the nrpe command would check the network device with snmpget (usually)).

Passive checks for network devices is usually done with snmp traps. If the device can route to the nagios server, then you could send traps to nagios. If it cannot reach the nagios server, you would need to use a trap forwarder to do so, but this will require rewriting the traps when the get forwarded to nagios so that they reference the host/service object in nagios, and not the proxy.

Windows boxes, again, can use a proxy nrpe server active checks, or use passive means. To passive check, you could use nsclient, send_nsca_win32, or nrdp/nrds.

Thanks abrist. So as I understand it, active check is used when the Nagios server belongs to the same subnet as the device or server that will be monitored. So if we have our Nagios server in another domain from the servers and devices that it will monitor, we have to use passive checking. As you have mentioned, we can use nsclient, send_nsca_win32, or nrdp/nrds to monitor remote servers with passive check. Is nrdp/nrds the only available add-on for Nagios Core?

Passive checks for network devices is usually done with snmp traps. If the device can route to the nagios server, then you could send traps to nagios. If it cannot reach the nagios server, you would need to use a trap forwarder to do so, but this will require rewriting the traps when the get forwarded to nagios so that they reference the host/service object in nagios, and not the proxy.

As for the network devices, may I request for a reference/documentation I can follow prior to the test and configuration you mentioned above?

Thank You,

Arnel

Noctis0791 wrote:So if we have our Nagios server in another domain from the servers and devices that it will monitor, we have to use passive checking

It is only required if the nagios server cannot route to/from the subnet.

Noctis0791 wrote: Is nrdp/nrds the only available add-on for Nagios Core?

They are technically agent protocols, and they are just a couple among a very large number of nagios agents.

Noctis0791 wrote: As for the network devices, may I request for a reference/documentation I can follow prior to the test and configuration you mentioned above?

First of all, you will need to make sure your networking devices support snmp and that they have been configured with a community string (or setup to send traps to the nagios ip).

Hi abrast,

Just to confirm. How do we test the route for the remote servers and network devices, will a simple PING do? If that is the case, then if we can PING the remote server or the remote network device from our Nagios Core server, we can use active checking, is that correct?

May we also know what are the recommended agent protocols we can use for Windows for both active and passive check?

As for the remote devices, I would still need to confirm if they support snmp. But if they do and we can route to them from our Nagios server, that means less configuration because we just have to configure the community string on them, is that right?

Thanks for being patient with me,

Arnel

I'd recommend using NMAP to check the routs between your nagios server and your remote hosts. Just because you can ping or rout to them does not mean you can or want to use active checks. You can use passive or active.

As far as Windows goes you can check out NCPA which is our new active/passive all in one agent:

http://assets.nagios.com/downloads/ncpa ... g_NCPA.pdf

And of course there is still NSClient++ which uses a mix of NRPE, NSCA, and check_NT checks:

http://assets.nagios.com/downloads/nagi ... _Agent.pdf

As far as passive checking goes, you can use anything from SNMP Traps, to NRDP, there are quite a few options available.

Hi slansing,

Thanks for your helpful response. May I just ask what test should I run using NMAP and what result should I look for to see that I can use active check for the remote hosts. Ive installed nmap-6.40-setup.exe and I have the following option for the scan.

Intense scan
Intense scan plus UDP
Intense scan, all TCP ports
Intense scan, no ping
Ping scan
Quick scan
Quick scan plus
Quick traceroute
Regular scan
Slow comprehensive scan

As for NCPA, can I also use this for Nagios Core?

Thank You,

Arnel

You will want to install nmap on the nagios server so you can check if it can get through to your windows hosts. This is not necessary, I had just though you may have had it installed already. You can totally use NCPA with nagios core as well. The difference with XI and core using NCPA is that you will also have a wizard to make configuration easier in XI.

Yes, I understand that this is just for checking that’s why I installed NMAP on my local machine instead. I installed nmap-6.40-setup.exe (http://nmap.org/download.html) on my Windows machine. Now I don’t know which scan to run against the remote hosts and the result we are expecting to see if we can use active checks on them. Did I install the wrong one? If so, may I request the link for the correct one to install?

Thank You,

Arnel

Target: host IP
Profile: Quick scan

If it says "Host is up" you can at least ping it. Any open ports listed will almost certainly confirm you can send checks.

However, this will not check from the nagios server's perspective, as slansing said. Your local Windows machine may be able to reach a machine while your Nagios server may not.