As mentioned above, I need to install only the mongo shell on a RHEL instance (machine A). I have a mongodb server on a separate instance (machine B) and need to connect to that
sudo vim /etc/yum.repos.d/mongodb.repo
[mongodb-org-4.0] name=MongoDB Repository baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/4.0/x86_64/ gpgkey=https://www.mongodb.org/static/pgp/server-4.0.asc gpgcheck=1 enabled=1
sudo yum clean all
sudo yum install mongodb-org-shell-4.0.2
mongo
Note: Step 4 will not work in all cases. You need to check proper command to connect to remote mongo server.
Source: https://docs.mongodb.com/manual/tutorial/install-mongodb-on-red-hat/