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I can connect to google, but not to duckduckgo.

$ ping google.com
PING google.com(arn09s19-in-x0e.1e100.net (2a00:1450:400f:80c::200e)) 56 data bytes
64 bytes from arn09s19-in-x0e.1e100.net (2a00:1450:400f:80c::200e): icmp_seq=1 ttl=116 time=15.4 ms
64 bytes from arn09s19-in-x0e.1e100.net (2a00:1450:400f:80c::200e): icmp_seq=2 ttl=116 time=16.5 ms
^C
--- google.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 15.362/15.916/16.471/0.554 ms
$ ping duckduckgo.com
ping: connect: Network is unreachable

I think that's because google has ipv6 and duckduckgo hasn't, as shown by nslookup.

$ nslookup google.com
Server:     127.0.0.53
Address:    127.0.0.53#53

Non-authoritative answer:
Name:   google.com
Address: 216.58.207.238
Name:   google.com
Address: 2a00:1450:400f:80c::200e

$ nslookup duckduckgo.com
Server:     127.0.0.53
Address:    127.0.0.53#53

Non-authoritative answer:
Name:   duckduckgo.com
Address: 52.142.124.215

The same applies for facebook.com which has ipv6 and works, and github.com wich hasn't and doesn't.

I bought an internet cable which plugs directly to the router, and the problem stayed. But when I turn off wifi, unplug the cable and use USB-thetering via my Android smartphone everything works fine (the smartphones mobile data is turned off and it is connected to the wifi). My flatmates have no connectivity problems on their devices. I used the computer for one year now and the problem only started this morning.

Is there something I can do?

Solutions I tried

I looked at this post. The proposed solution was to disable ipv4 in the wifi's graphical configuration, and setting "Method" to "Automatic, addresses only" in ipv6 the wifi's settings. I don't have this option in my settings, and setting it to "Automatic" or "Automatic, addresses only" didn't change anything.

I also tried this solution

$ sudo dhclient -r wlp2s0
Killed old client process
$ sudo dhclient wlp2s0

That didn't solve the problem but changed ping's error message:

$ ping duckduckgo.com
PING duckduckgo.com (52.142.124.215) 56(84) bytes of data.
From _gateway (192.168.1.1) icmp_seq=10 Destination Net Unreachable
^C
--- duckduckgo.com ping statistics ---
32 packets transmitted, 0 received, +1 errors, 100% packet loss, time 31690ms

Edit

usb0 is my Android device.

Output of ip route:

$ ip route
default via 192.168.42.129 dev usb0 proto dhcp metric 100 
default via 192.168.1.1 dev wlp2s0 proto dhcp metric 600 
169.254.0.0/16 dev wlp2s0 scope link metric 1000 
192.168.1.0/24 dev wlp2s0 proto kernel scope link src 192.168.1.33 metric 600 
192.168.42.0/24 dev usb0 proto kernel scope link src 192.168.42.224 metric 100 

Output of route

$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         _gateway        0.0.0.0         UG    100    0        0 usb0
default         _gateway        0.0.0.0         UG    600    0        0 wlp2s0
link-local      0.0.0.0         255.255.0.0     U     1000   0        0 wlp2s0
192.168.1.0     0.0.0.0         255.255.255.0   U     600    0        0 wlp2s0
192.168.42.0    0.0.0.0         255.255.255.0   U     100    0        0 usb0

output of ifconfig:

$ ifconfig
enx00e04e3a4476: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.36  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 2001:4646:58b8:0:1de0:9fed:a9ea:a5d7  prefixlen 64  scopeid 0x0<global>
        inet6 fe80::a9bd:79ab:e302:83ff  prefixlen 64  scopeid 0x20<link>
        inet6 2001:4646:58b8:0:bec2:942:e66:f0da  prefixlen 64  scopeid 0x0<global>
        inet6 2001:4646:58b8:0:cd74:eed2:2eb2:e437  prefixlen 128  scopeid 0x0<global>
        ether 00:e0:4e:3a:44:76  txqueuelen 1000  (Ethernet)
        RX packets 315  bytes 38645 (38.6 KB)
        RX errors 0  dropped 3  overruns 0  frame 0
        TX packets 468  bytes 62610 (62.6 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 12520  bytes 1072501 (1.0 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12520  bytes 1072501 (1.0 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

usb0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.42.239  netmask 255.255.255.0  broadcast 192.168.42.255
        inet6 fe80::732b:158e:d3d9:4409  prefixlen 64  scopeid 0x20<link>
        ether 96:bf:5c:93:c0:7a  txqueuelen 1000  (Ethernet)
        RX packets 1370  bytes 426638 (426.6 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1581  bytes 412547 (412.5 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.33  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 fe80::6f50:6f2d:d7a8:f848  prefixlen 64  scopeid 0x20<link>
        inet6 2001:4646:58b8:0:650e:8cfb:7323:d714  prefixlen 64  scopeid 0x0<global>
        inet6 2001:4646:58b8:0:15bb:278d:a998:f4d  prefixlen 128  scopeid 0x0<global>
        inet6 2001:4646:58b8:0:d72d:2a87:de99:4f79  prefixlen 64  scopeid 0x0<global>
        ether 74:c6:3b:7f:3c:e9  txqueuelen 1000  (Ethernet)
        RX packets 78154  bytes 52156567 (52.1 MB)
        RX errors 0  dropped 4424  overruns 0  frame 0
        TX packets 32789  bytes 4744530 (4.7 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
2
  • Your gateway does not provide IPv4-connectivity. This is not a Ubuntu-problem from what you post.
    – vidarlo
    Mar 2, 2021 at 17:01
  • @vidarlo Sorry I was not precise enough. The smartphone is connected to the wifi, and my flatmates computers can load duckduckgo.com (I juste edited the question).
    – Louis
    Mar 2, 2021 at 17:10

1 Answer 1

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Answering my own question

Counterintuitively it was the router, not Ubuntu. I find it counterintuitive because internet worked on all other devices (my smartphone and my flatmates computers) connected to it. However one flatmate just got the same problem, so it has to be the router.

Conclusion

If a router works for all devices except yours it doesn't necessarily mean that it's your devices' fault.

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