My work environment has heavily restricted access to the outside from any of our machines. I am often spinning up new Linux machines for testing purposes and getting temporary firewall access to a specific IP is a process I do not enjoy. As a work around, I have tunneled my YUM updates and Repos through machines that do have Repo access.
From the machine with restricted access edit your /etc/yum.conf file adding the following line. xxxx = the unused high port of your choice.
From a separate terminal type the following at the prompt.
ssh -ND xxxx username@server-with-access
This will leave you with what appears to be a hung session with an unresponsive prompt. a simple Ctrl-c will kill the tunnel. As long as the session is live, you can run your yum update from a separate session.