Router periodically turning off every 2 hours
I just got AT&T fiber installed two days ago and have been experiencing some inconsistent router connection issues ever since I attempted an IP Passthrough from my Arris BGW210-700 to my Nighthawk R7000P router. Everything works well until the 2 hour mark comes up and the router would disconnect and connect again. I'd get a log like this every time from my Nighthawk router (this is my most recent one):
[DoS attack: FIN Scan] attack packets in last 20 sec from ip [X], Monday, Jun 15,2020 12:11:37
[DHCP IP: (X)] to MAC address X, Monday, Jun 15,2020 12:11:35
[Time synchronized with NTP server] Monday, Jun 15,2020 12:11:28
[Internet connected] IP address: X, Monday, Jun 15,2020 12:11:23
[Internet disconnected] Monday, Jun 15,2020 12:11:22
The BGW210-700 connection is always up and running - there's no issue with that. It's just my Nighthawk router that's periodically dropping the connection.
I understand that there's no "true bridge mode" and tried researching alternative methods but to no avail (e.g. making sure there's a different subnet). I'm assuming there's a double NAT issue at play here?
Any suggestions are appreciated - Thank you!