Dell XPS 15 Service Manual page 108

NOTE: Some ISPs (Internet Service Providers) provide a modem/router combo device.
1 Turn off your computer.
2 Turn off the modem.
3 Turn off the wireless router.
4 Wait for 30 seconds.
5 Turn on the wireless router.
6 Turn on the modem.
7 Turn on your computer.
108 Troubleshooting