How to check Host is up with Nagios for servers
with disabled ICMP (ping) protocol
At the company where I administrate some servers, they're running
Nagios to keep track of the servers status and instantly report if
problems with connectivity to certain servers occurs.
Now one of the servers which had configured UP host checks is up,
but because of heavy ICMP denial of service attacks to the servers
the ICMP protocol ping is completely disabled.
In Nagios this host was constantly showing as
DOWN in the
usual red color, so nagios reported issue even though all services
on the client are running fine.
As this is quite annoying, I checked if Nagios supports host
checking without doing the ICMP ping test. It appeared it does
through something called in nagios
Submit passive check result
for host
Enabling the
"Submit passive check result for this host"
could be done straight from Nagios's web interface (so I don't even
have to edit configurations! ;).
Here is how I did it. In Nagios I had to navigate to:
Hosts -> Click over my host (hosting1) which showed in red
as down
You see my down host which I clicked over showing in red in above
pic.
On next Nagios screen I had to select,
Disable active checks of
this host
and press on the
Commit button.
Next following text appears on browser:
Your command request was successfully submitted to Nagios for
processing.
Note: It may take a while before the command is actually
processed.
Afterwards I had to click on
Submit passive check result for
this host and in:
Check Output to type in:
check_tcp -p 80
Here is the Screenshot of the
Command Options dialog:
That's all now Nagious should start checking the down host by doing
a query if the webserver on port 80 is up and running instead of
pinging it.
As well as the server is no longer shown in the Nagio's
Down
host list.