Nagios Updated a host but old host is still pinged

I have a nagios item which is a switch that I have changed the IP on in
hosts.cfg but the old host keeps getting pinged insted.

Is hosts.cfg the correct file to edit to update an item when the IP has
changed.

Also Nagios is installed on Red Hat and I would like to migrate it to
Debian, I have tried to copy the required files but the versions in Nagios
are too different to accept the nagios.cfg file, what would be the best way
to migrate a Nagios install from Red Hat to Debian?



Jim