Is SNMP a solution

[usa ims]

I have a xymon server located out in the Internet that uses custom scripts for monitoring.
I monitor this one server which is NATed behind a firewall. I use 'xymon-rclient.sh' script to fetch the data. This server is only one that is exposed on the internet, it has an IP of 192.169.100.50.
But I want to monitor it's sister server '192.168.100.51' which is not exposed on the Internet.
Somebody said to me that SNMP might be a solution.
If that is a solution, can somebody give me a high level explanation on how this might work?
Thanks in advance.
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