I wrote:
For a primary interface with a static address, I may be able to add the information as IPADDR2 (etc) in ifcfg-eth0. But how do I do this if the primary interface gets its address via DHCP?
Samuel Sieb answered:
Install "nm-connection-editor". It gives you a lot more capabilities, including doing that.
I've tried that and it doesn't. When the connection method is DHCP, the additional address area is grayed out.