Check Locally

I’m not sure if this is the right forum to post this but here goes

I set up 4 servers and using a localserver have set up nagios to monitor the servers remotely from my pc with nagios. problem is I’ve set up 2 servers as web and the other 2 as databases and connected them on a local network. i need to use nagios to monitor all of them,
configuration is as follows

Server1
eth0 60.102.99.121
eth1 192.168.100.1

Server 2
eth0 60.102.99.122
eth1 192.168.100.2

DB1
eth0 192.168.100.3

DB2
eth0 192.168.100.4

my hosts.cfg contains
define host{
use generic-host
host_name Web1
alias Web1 Server
parents LocalServer
address 60.102.99.121
check_command check-host-alive
contact_groups admins
}

define host{
use generic-host
host_name Web2
alias Web2 Server
parents LocalServer
address 60.102.99.122
check_command check-host-alive
contact_groups admins
}

But i don’t know how to check for the databases? how do i sonfigure nagios to check pcs connected in that local network?
how do i go about it?
thanks i really appreciate it