For CentOS 7.7 access, "ssh ifarm.jlab.org" to reach the interactive nodes ifarm1801, ifarm1802, and ifarm1901.jlab.org:
You are free to use these nodes for software development and testing, but do not run long tasks interactively.
These interactive machines are not accessible from offsite; you will first need to "ssh login.jlab.org". Similarly, the interactive nodes can't reach offsite nodes.