Here is a good reference SSH config file for OpenSSH client
From a secured server, I am able to connect to 2 different environments which seems counter intuitive but I digress.
Since there are 2 different environments, the same ~/.ssh/config cannot be used as there may be IP overlap.
One environment will use ~/.ssh/config and ssh emhost
Other environment will use ~/.ssh/cbconfig and ssh -F ~/.ssh/cbconfig emhost
The default EM port for both hosts is 7803.
Using firefox https://localhost:7803/em to access EM does not work well when saving username and password as they will be overwritten.
One solution to save sysman’s password is to use URL with different port.
Hence, config will have EM port 7803 forward to 7803 while cbconfig will have EM port 7803 forward to 7804.

========================================
This is on cloud and looks complicated.
========================================
I did not create the configuration and don't know how many hours it took.
~/.ssh/config
Host emhost
HostName 10.157.38.66
LocalForward 7001 10.157.38.66:7001
LocalForward 7102 10.157.38.66:7102
LocalForward 7803 10.157.38.66:7803
LocalForward 9803 10.157.38.66:9803
LocalForward 9851 10.157.38.66:9851
# DEFAULTS:
Host *
User dinh
========================================
This is on premise and looks simpler.
========================================
ssh -F ~/.ssh/cbconfig emhost
Host emhost
HostName 10.10.72.254
# Forward port need to use IP address.
# Equivalent to ssh -L 7804:10.10.72.254:7803 mdinh@10.10.72.254
LocalForward 7804 10.131.28.227:7803
# DEFAULTS:
Host *
User mdinh