I was thinking just swapping the /etc/resolv.conf. It says not to do that in the header. They are a mix of RHEL 6/7, Centos 5/6/7 and Oracle Linux 6/7.
I was thinking some have DNS1=xx.xx.xx.xxx in the ifcfg-eth0 BUT not all call it eth0 - some are em1, I'm thinking even others might be something else slightly different.
So then I thought search for DNS in ifcfg-* and if you find DNS1 sset to to this, if DNS2, set it to that...
Kind of complicated. I have about 50 set up with Ansible.
Does anyone have a playbook setup for this already or can point me to a good resource?