I will be monitoring remote sites and I’m assuming the best way is to build a ipsec tunnel between all locations and the firewall that is in front of the nagios server. Does anyone have any experience doing this? If so, what hardware did you use at the remote sites to establish the ipsec tunnel?
you don’t even need that, remote servers can encrypt the traffic with different algorithms.
Never done it before, just thinking out loud 
I did not realize that! Thanks! This would require a remote server at each site though. I am trying to figure out if it would be cheaper to place a server at every location or tunnel the traffic back to a centralized server through some sort of vpn/firewall device.
you would need much more than a server at each remote location for creating the tunnels and such… If you don’t already have them… i suppose you already have the firewalls… you may as well create rukles to permit the checks from the server to the hosts to be minitored without any particular problems… personaly i don’t see a need to encrypt the checks… Depends on what type of security you are looking for.