DNS server shows IPv6 instead of IPv4 for Ethernet adapter and Ethernet not working

Question

Recently my Ethernet stopped working and when I ran ipconfig /all, it showed IPv6 addresses for the DNS servers instead of the usual IPv4. I don't know what the problem is and I can't find a solution on how to make it switch back to IPv4.

I don't remember making any changes to my computers network settings although I was coding with sockets earlier but that was over WiFi so I don't think that could have affected the Ethernet settings.

I have also tried uninstalling and reinstalling the driver and rebooting my computer but none of that seems to fix the problem. Any solutions?

DNS Servers . . . . . . . . . . . : 
fec0:0:0:ffff::1%1
fec0:0:0:ffff::2%1
fec0:0:0:ffff::3%1

Solution 1

I had the same problem just right now. The system is Windows 7 but 10 has the same issue. On 7 the WiFi adapter gets IPv4 address and correct default gateway but it gets weird ipv6 DNS addresses.

By the way I'm using 1.1.1.1 and 1.0.0.1 as DNS servers.

I tried with ipconfig /flushdns, but it did not work. The way it fixed was like this:

• Go to properties on your WiFi adapter
• Disable the checkbox on IPv6 and hit OK
• Disable and enable the adapter (it was still not working for me, ipconfig shows no DNS at all)
• Then go to properties again and tick the checkbox for IPv6 and hit OK
• Disable and enable the adapter once again (after this it is working now)

Solution 2

Your Ethernet adapter config suggests a possible DHCP issue. DHCP is enabled on the client, but your IPv4 address is an APIPA address, suggesting that the client was unable to receive an address from the DHCP server. That would explain why the IPv6 addresses are listed for DNS Servers. Client often receive default gateway and DNS information via DHCP scope options.

The IPv6 addresses you listed are reserved site-local addresses (RFC 3879), which is deprecated, but for some still employed in cases like this. I hesitate to compare site-local addressing directly with APIPA, as link-local addresses are a closer comparison.

I was able to dig up an interesting article on site-local addresses. It explains the relationship between site-local addresses and DNS in more depth.

https://www.howfunky.com/2015/10/ipv6-site-local-addresses-why-are-those.html

All that to say, I would start looking at DHCP.

Solution 3

There's something clearly wrong with your network. Your ipconfig output shows a link local address which essentially means you aren't getting an IP address at all. The fec0 addresses are the IPv6 equivalent of 169.254.x.x ( address which occur when you have some network connectivity, but there are issues with getting an IP address.

There are a few possibilities - there's something wrong with the IPv4 settings (double check these!) or your Ethernet adapter is borked. In this case, since you're not getting an IP address (which is the real issue), we can probably start there.

I'd try the Ethernet adapter with static settings as well. Since DHCP leases last a while renewing leases or restarting your router would be an idea.

Comments

[Seth]

Why do you assume the IPv6 address of the DNS server is the problem?

[J leong]

@Seth because I have googled it and I found one post where someone had ipv6 under the dns servers and their internet wasn't working. also under my wifi it is ipv4 for the dns servers

[Seth]

What version of Windows are you using? Does your client have an IPv4 or IPv6 address? What do you mean your Ethernet doesn't work? You LAN internet connection? Can you reach other clients on the network?

[J leong]

@Seth i am unable to connect to the internet via ethernet cable. it shows those things under dns servers in the ipconfig /all. I don't know if it works over LAN. there is also no default gateway for the ethernet.

[Daniel B]

Sounds like your DHCP server isn’t working. Please provide the entire output of ipconfig /all, preferably only for the relevant network interface.

[J leong]

@DanielB i added the output

[Daniel B]

You could’ve just copied the text, but whatever. Your Ethernet connection isn’t getting an address from DHCP. That’s why it isn’t working. Windows calls this state “Limited connectivity”. Also, your internal IP addresses are not confidential information.

[J leong]

@DanielB ok but then how would I resolve this issue? the cable works with my friend's laptop so the problem has to be my computer.

[J leong]

oh wait nevermind i fixed it. i restarted my dhcp server as soon as you said that it could be a problem with that. Thanks for all your help Daniel!

[kasperd]

What I find even more suspect is that it uses Cloudflare as DHCP server.

[will824]

This is exactly what solved the DNS problem for me as well. Somehow this problem seems to happen in latest Windows 10 versions when you have Hyper-V Virtual Network Adapters. Seems that the WiFi adapter tries to use the IPv6 DNS.