RHEL7 / CentOS7 network interface going down once per hour

There's really bizarre bug in RHEL7 / CentOS7. Once per hour NetworkManager will remove IP addresses from ethernet interface after hitting some bug and triggering "link loss" action. Interface may come back by itself or may not. It does come back when you login as root on console as login triggers some repair action part via systemd...

Migrating user accounts from older Linux to RHEL7 / CentOS7

Another pointless change just to break backwards compatibility - RHEL7 and CentOS7 prevent users with uid lower than 1000 from logging in. This is bad when you're migrating accounts from existing Linux server where uids start at 500.

RHEL7 / CentOS7 with sshd on ports 22 and 443

Short version: Not as simple as you thought.