I have a RUT240 modem serving WiFi to a laptop. Under normal conditions, the laptop gets a 192.168.1.x IP address, which is what I configured. Life is good.
The RUT240 modem is connected to mobile (sim card, LTE) and to WAN (ethernet connection).
Sometimes when I reboot the RUT240, by removing the external power and NOT by using the Web UI, the laptop gets an IP address in a range that is NOT 192.168.1.x, but in the range of the EXTERNAL WAN connection. This is as if the router is acting in bridge mode for some unknown reason. It can be there for 30 minutes or so.
In this scenario I have no way of loading the UI of the rut modem since it is configured to listen on the inside network and surely enough 192.168.1.1 does not work anymore.
I reboot the RUT240 several times and then it comes back to normal: the laptop gets an IP in the 192.168.1.x range, I can open the UI and life is good again.
What can be going on here?
Some observations below.
ipconfig of the laptop when it has a "normal" IP address:
Wireless LAN adapter Wi-Fi 2:
Connection-specific DNS Suffix . : lan
Link-local IPv6 Address . . . . . : fe80::810:c5fe:df5d:70e%17
IPv4 Address. . . . . . . . . . . : 192.168.1.234
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
ipconfig of the laptop when the rut240 is "Acting up":
Wireless LAN adapter Wi-Fi 2:
Connection-specific DNS Suffix . : somecorp.com
Link-local IPv6 Address . . . . . : fe80::810:c5fe:df5d:70e%17
IPv4 Address. . . . . . . . . . . : 192.168.216.36
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.216.1
somecorp.com is the name of the corporate network where the router is connected via ethernet, its WAN interface.
If I connect the laptop to this corporate network directly via ethernet (no modem involved) the laptop gets an IP address in that range (192.168.216.x) with an identical C.S. DNS Suffix.
What could be going on here?
I have NOT configured the router to become a bridge (as far as I know).
Thanks!
PS: removing the power is a robustness test of this setup.