Hi,
I'n new to Nagios, however have installed Nagios Core and monitoring about 19000 switches. They are all grouped into 6 host groups. when i try to pull out a report of a particular hostgroup i get the report but when i try for all hostgroups, i get an error that says: Internal Server Error.
Pls help!
Without the webserver error log, it's a guess as to the cause, but I'd say you will want to look at your php limits in /etc/php.ini You are probably blowing out some memory limit someplace as it tries to compile everything into one giant list.
Failing that, try finding the error in your webserver logs and see what it's telling you.