[Frage] Second LAN ip address

I would like to add a second IP address to the lan interface.
To do this I thought I can use the already present lan:0 interface.

On startup I have in rc.local:
But I observe that, after some time (about a day) the interface get reset to 169.254.1.1

Can I prevent the lan:0 interface to be reset to 169.254.1.1, or is there another way to add a second IP address?