The bin update will also delete the certificates directory, firewall setting, etc, right? I need a backup asap, before to go with the update
It's a good idea to import a backup after the update or it's better to make again all the configurations by hand?
I'm actually using a usb stick for extroot
You can either choose to create a backup and restore it, or choose the checkbox to keep-settings. However, I would recommend doing neither, and doing a fresh install (not keeping your existing configuration because of the reasons below).
As I said in my previous post, I believe you are getting the 192.168.1.1 IP showing on eth0.1 because of the improper way you have ModemTI interface configured...it is confusing the router.
You need to make a new LAN VLAN (such as eth0.3) for ModemTI. You can't simply assign it to eth1.2 with wan and wan6 because ModemTI is a LAN link, not a WAN link (Even though the modem is the source of your internet and connected to the WAN port, the way you are trying to access it via a static address requires a LAN link/VLAN in addition to the WAN link (eth1.2) for your internet). Also, this improper configuration is most likely opening a giant hole in your firewall. I'm 99% sure this unstable configuration is confusing the router and generating the 192.168.1.1 IP for eth0.1 even though it is part of br-lan which has the desired 192.168.2.1 IP.
I would highly recommend just leaving the router/LEDE settings as defaults and simply changing the modem's IP to 192.168.1.2, or even 192.168.100.1 (if it allows that). Every cable modem I've ever seen has the IP set to 192.168.100.1, including mine, and I can easily access it without changing any configuration in LEDE.
Linksys WRT1200AC V1
running LEDE snapshot branch (@davidc502's newest build)
upgraded with latest package versions from LEDE distro feeds