Dell Precision 7550 Service Manual page 101

NOTE: Some ISPs (Internet Service Providers) provide a modem/router combo device.
Steps
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.
Troubleshooting 101