When I was helping a friend with one of the small networks for which he is responsible, I notice the DPC3939B gateway on one of his networks had bridge mode disabled, had private WiFi (2.4GHz and 5GHz) enabled, and the DHCP service and UPnP were enabled. The private WiFi networks were default configurations as far as I know--this network otherwise uses AirPort and AirPort Extreme for WiFi, with WiFi settings (SSID, etc) different from the gateway's WiFi settings.
Anyway, my friend agreed with my recommendation to disable WiFi on the DPC3939B and disable the DHCP server and UPnP and enable bridge mode. Between the gateway and LAN is a SonicWALL TZ215.
I first disabled WiFi, DHCP and UPnP, then enabled bridge mode. After the gateway applied the settings, we lost Internet access. I tried power cycling first the gateway then the TZ215--this made no difference. I think I need to adjust the WAN configuration on the TZ215, but I'm not entirely certain what needs to change. The TZ215 WAN interface is configured for the correct static public IP address. The default gateway address for the WAN interface is a public IP address which I happened to notice was the public IP address assigned to the Xfinity gateway when it was in router mode. I'm guessing I need to set this default gateway setting differently, but how / to what? Any other suggestions?
Thank you!