Here is why:
A Complete Guide to Red Hat Enterprise Linux 7.3 ISO Download
This is a crucial point: , as it is no longer receiving any security updates.
: If you are using RHEL for personal, non-production development, you can join the Red Hat Developer Program Register for a no-cost developer account
Mount the ISO to a directory: mount -o loop rhel-server-7.3-x86_64-dvd.iso /mnt/
What are you installing this on?