Ping Using IPv4 on Laptop Not Working, IPv6 Fine

#1

I’m encountering a strange issue on my laptop on my home wifi network.

From my laptop, pinging over IPv6 is working great:

λ ping google.com

Pinging google.com [2607:f8b0:4005:804::200e] with 32 bytes of data:
Reply from 2607:f8b0:4005:804::200e: time=15ms
Reply from 2607:f8b0:4005:804::200e: time=14ms
Reply from 2607:f8b0:4005:804::200e: time=17ms
Reply from 2607:f8b0:4005:804::200e: time=14ms

Ping statistics for 2607:f8b0:4005:804::200e:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 14ms, Maximum = 17ms, Average = 15ms

But IPv4 is not working at all:

λ ping -4 google.com

Pinging google.com [216.58.195.78] with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.

Ping statistics for 216.58.195.78:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

Traceroute using IPv4 is totally failing too:

λ tracert -4 google.com

Tracing route to google.com [216.58.195.78]
over a maximum of 30 hops:

  1     *        *        *     Request timed out.
  2     *        *        *     Request timed out.

I can’t even ping the router:

λ ping 192.168.0.1

Pinging 192.168.0.1 with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.

Ping statistics for 192.168.0.1:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

ipconfig shows the interface as having an IPv4 address:

Wireless LAN adapter Wi-Fi:

   Connection-specific DNS Suffix  . : hsd1.ca.comcast.net.
   IPv6 Address. . . . . . . . . . . : 2601:647:5a01:a670:7de3:6143:1811:de22
   Temporary IPv6 Address. . . . . . : 2601:647:5a01:a670:24b2:da1c:386b:3bd3
   Link-local IPv6 Address . . . . . : fe80::7de3:6143:1811:de22%4
   IPv4 Address. . . . . . . . . . . : 192.168.0.16
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : fe80::ce40:d0ff:febf:67e2%4
                                       192.168.0.1

Going to sites that are IPv4-only works fine (eg. this site seems to be IPv4-only, but I can see it fine, and I can also load the router’s web UI). It just seems to be ICMP that’s having issues.

Any ideas on how to debug this?

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#2

This also sometimes happened to me as my ISP uses DSlite and thus doesn’t allocate a public IPv4 to me, only IPv6 and a sorta tunnel to IPv4. So when I have IPv4&6 enabled on my router it will try to only use IPv6 (also for ping like your case atm). However once I disable IPv6 on my Router it pings in IPv4 :slight_smile:

I’m with Vodafone Germany btw.

That’s basically what DSlite is:

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#3

Interesting! I’ve got both native IPv4 and IPv6 (Comcast) though, so I don’t think that’d be it in my case.

Just noticed that it’s working again now… Huh. It seems like it works sometimes, but not other times.

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#4

Can you post your interfaces file?

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#5

I can’t, because I’m on Windows 10 :smiley:

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#6

Haha, that’s some early morning :man_facepalming: right there.

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#7

Alright, I vaguely remember having some similar problems on Win7 years ago. The fix was always to re-order interface provider priority, but that isn’t an option anymore in Win10 it seems. I found this Microsoft article: https://support.microsoft.com/en-us/help/929852/guidance-for-configuring-ipv6-in-windows-for-advanced-users

To save you from reading through it, here’s the command to create the reg-key to tell Windows to prefer IPv4 over IPv6: reg add "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters" /v DisabledComponents /t REG_DWORD /d 20 and then reboot after creating that, you might be able to get away with restarting the adapter/device, not sure.

This obviously doesn’t fix the root cause, but if this works then it stops that from ever occurring :slight_smile: probably some Windows fuckery. I just know that’s the fix for the same style of problem I had back then and I never bothered to dig deeper and try to understand yet another Microsoft mess.

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#8

This is my work laptop, and a lot of services I use at work (eg. development servers) are IPv6-only, so I’d be worried about breaking something by doing that :confused:

Just noticed that it works fine when connected to my work VPN, it’s just my home wifi that has the issue. I’ll try it with my desktop PC (which is connected via Ethernet) when I get a chance, and see if it has the same issue.

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#9

FWIW I never had such issues. I’d definitely give it a shot since it’s easy to revert (delete that reg key) if it does cause problems. It’d also be worth it just to confirm whether it is that type of functionality that is causing the problem or not.

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#10

Most likely because your work VPN doesn’t support IPv6 and thus forces IPv4.

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#11

Hmm, I’d assume his work VPN supports v6, they’re a pretty big proponent of v6 adoption - and as he mentioned, tons of their internal stuff is v6-only.

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#12

Fair enough.

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#13

His company is built using PHP technologies, and anyone who knows PHP can tell you-

It’s a lot easier to block IPv4 than 6 on an as-necessary basis.

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#14

Haven’t used PHP for many many years… It’s Hack now, which has removed a loooot of the bad parts of PHP.

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