Cannot change LAN ip address for cascading setup?

Hi. I'm trying to setup a cascading router across Ethernet. I need to change the secondary router's lan settings so it doesn't conflict, correct? However, everytime I change the ipv4 address and apply, it times out and rolls back. All other settings are default. Do I need to change the default gateway or protocol as well? They are currently empty and static address respectively. Thanks.

And after that roll-back, you have noticed also the button "Apply unchecked" ????
That forces applying your new setting even if breaks the current connectivity to your browser (which it does, as the router's IP changes)

Or you could do the things the old way, with an editor to the config file.

Alright thanks for that tip. Before I try again, can you confirm that changing the ipv4 address to 192.168.2.1 and nothing else should work with my setup? Sorry, I'm new to all of this. Thanks mate

No, I can't.
You have provided no clues about your setup, except that you have two routers...

How are they connected? what is your target setup?

192.168.2.1 would be from different subnet, so you are going for double-NAT or complex routing?

The simplest case for you might be the "dumb AP" recipe:
e.g.
Not accessible after disabling DHCP

They are connected by powerline Ethernet. I would also like to have a VPN setup on the second router. I assume a dumb Ap wouldn't work with that?

Not sure if it is applicable to your setup, but this worked for me.

I was setting up freshly flshed router and since my lan is 10.0.0.0/24 and default is 192.168.1.0/24 it had to be changed. When setting from luci I was able to setup address but as with you, it rolled back. My solution was to login to 192.168.1.1, change LAN address to 10.0.0.1 and than quickly change my IP to some from subset 10.0.0.1/24 (ie 10.0.0.10) and logged into 10.0.0.1 - the new address of router. No rollback occured.

tl;dr; Set new address and log in to router on the new address immediately. Don't wait for the 30 second confirmation.

This is an old thread. There are many other threads covering the confusion with this feature: Apply unchecked - Confusion