How do I change the ISP adapter?

Keep IP addressing and DNS automatic initially; isolate the second ISP and confirm an actual DNS failure before assigning a public DNS server.

Test the second ISP independently

1. Disconnect from the first ISP’s Wi-Fi and connect only to the second ISP.
2. Test the second Wi-Fi with another phone or computer:
   • No devices have Internet: restart the second ISP’s modem/router. If the problem remains, contact that ISP or the router vendor.
   • Other devices work: continue with the Windows checks below.
3. Open Command Prompt as administrator, then refresh the address and DNS cache:

ipconfig /release
ipconfig /renew
ipconfig /flushdns
ipconfig

Microsoft recommends DHCP because it automatically obtains the appropriate IP address and DNS settings when moving between networks.^1^

Determine whether DNS is the problem

From the ipconfig output, locate Default Gateway, then run these tests:

ping <Default-Gateway-address>
ping [IP Address]
ping microsoft.com
ipconfig /all | findstr /c:"DNS Servers"
ping <listed-DNS-server-address>

Interpret the results as follows:

• Default gateway fails: the PC is not communicating correctly with the second router.
• Gateway works but [IP Address] fails: this points toward an upstream Internet or routing problem, although some networks block ping. Confirm by trying websites.
• [IP Address] works but ping microsoft.com says “could not find host”: DNS resolution is failing.
• If microsoft.com resolves to an address but ping packets time out, that alone does not establish a DNS failure; the destination may simply block ping.
• Microsoft’s diagnostic procedure also recommends identifying the configured DNS server and attempting to ping it.^2^

Change only DNS, not the IP address

Do not copy the current DHCP address into a static configuration. That can create an address conflict or leave settings from one ISP active when connecting to another.

1. Press Windows+R, enter ncpa.cpl, and select OK.
2. Right-click Wi-Fi → Properties.
3. Select Internet Protocol Version 4 (TCP/IPv4) → Properties.
4. Leave Obtain an IP address automatically selected.
5. Select Use the following DNS server addresses and enter one pair: Cloudflare
   • Preferred: [IP Address]
   • Alternate: [IP Address]
   or Google
   • Preferred: [IP Address]
   • Alternate: [IP Address]
6. Select OK, reconnect to the second Wi-Fi, and test browsing and Speedtest again. These public DNS pairs are documented as a troubleshooting option when DNS continues to fail.^3^

This classic setting applies to the Wi-Fi adapter generally, not as an independent “ISP 1 DNS/ISP 2 DNS” switch. After testing, return to the same dialog and select Obtain DNS server address automatically, especially if each ISP supplies its own DNS through DHCP.

On Windows versions exposing a separate DNS server assignment control under Settings → Network & internet → Wi-Fi → network properties, that control can also be used. Avoid changing IP assignment to Manual solely to test DNS, because that requires valid IP, subnet, and gateway values.^1^

If public DNS does not help

• Go to Settings → Network & Internet → Proxy and disable any unintended manual proxy.
• Disconnect any VPN temporarily.
• If only this PC fails, run Microsoft’s complete network reset sequence from an elevated Command Prompt:

netsh winsock reset
netsh int ip reset
ipconfig /release
ipconfig /renew
ipconfig /flushdns

Restart Windows afterward. These commands reset Winsock/TCP-IP, renew the DHCP lease, and clear the DNS resolver cache.^2^

References

1. Essential Network Settings and Tasks in Windows | Microsoft Support
2. [Windows 10](https://support.microsoft.com/windows/experience/connectivity-networking/fix-wi-fi-connection-issues-in-windows#most-common-wi-fi-problems)
3. No internet after windows update last week - Microsoft Q&A