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Thread: Network connected but no internet connection

  1. #1
    Join Date
    Oct 2005
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    38

    Network connected but no internet connection

    Hi

    I have a headless Ubuntu desktop running as a file server/minecraft server/media server, etc., and it just generally works. I've just tried going online and have found I can't connect. I can VNC into it and can connect via SSH. I can ping my router, but can't get out onto the internet at all. I've found several post where people have had similar issues but they all seem quite specific. I've tried the various solutions, but none have worked for me. Hopefully someone will be able to help? I'm sure you will ask for a lot of information, but here are the basics:

    I have two connections - ethernet and wireless. Both are active and have a valid IP Address. As mentioned above I can ping my router, other machines on the network, but just can't get out (ping 192.168.4.100/192.168.8.100/8.8.8.8/etc).

    ifconfig:
    Code:
    eth0      Link encap:Ethernet  HWaddr 6c:f0:49:2c:34:e2
              inet addr:192.168.1.109  Bcast:192.168.1.255  Mask:255.255.255.0
              inet6 addr: fe80::6ef0:49ff:fe2c:34e2/64 Scope:Link
              UP BROADCAST RUNNING MULTICAST  MTU:1492  Metric:1
              RX packets:3358420 errors:0 dropped:0 overruns:0 frame:0
              TX packets:4317457 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:1000
              RX bytes:2414538065 (2.4 GB)  TX bytes:4643393799 (4.6 GB)
              Interrupt:41 Base address:0xc000
    
    lo        Link encap:Local Loopback
              inet addr:127.0.0.1  Mask:255.0.0.0
              inet6 addr: ::1/128 Scope:Host
              UP LOOPBACK RUNNING  MTU:16436  Metric:1
              RX packets:594849 errors:0 dropped:0 overruns:0 frame:0
              TX packets:594849 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:0
              RX bytes:55785926 (55.7 MB)  TX bytes:55785926 (55.7 MB)
    
    wlan0     Link encap:Ethernet  HWaddr 00:02:72:52:d4:a4
              inet addr:192.168.1.107  Bcast:192.168.1.255  Mask:255.255.255.0
              inet6 addr: fe80::202:72ff:fe52:d4a4/64 Scope:Link
              UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
              RX packets:190168 errors:0 dropped:0 overruns:0 frame:0
              TX packets:73577 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:1000
              RX bytes:40093655 (40.0 MB)  TX bytes:79052757 (79.0 MB)
    iwconfig:
    Code:
    lo        no wireless extensions.
    
    wlan0     IEEE 802.11bg  ESSID:"linksys"
              Mode:Managed  Frequency:2.462 GHz  Access Point: 00:16:B6:B7:94:10
              Bit Rate=48 Mb/s   Tx-Power=20 dBm
              Retry  long limit:7   RTS thr:off   Fragment thr:off
              Power Management:off
              Link Quality=70/100  Signal level=70/100
              Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
              Tx excessive retries:3  Invalid misc:169   Missed beacon:0
    
    eth0      no wireless extensions.
    route -n:
    Code:
    0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 eth0
    169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 eth0
    192.168.1.0     0.0.0.0         255.255.255.0   U     1      0        0 eth0
    192.168.1.0     0.0.0.0         255.255.255.0   U     2      0        0 wlan0
    sudo gedit /etc/resolv.config:
    Code:
    # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
    #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
    nameserver 194.168.4.100
    nameserver 194.168.8.100
    nameserver 127.0.0.1
    search cable.virginmedia.net
    sudo gedit /etc/network/interfaces:
    Code:
    auto lo
    iface lo inet loopback
    Let me know what else you need - any help greatly appreciated!
    Last edited by Tass; December 28th, 2013 at 02:08 AM.

  2. #2
    Join Date
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    Re: Network connected but no internet connection

    I've seen another thread with similar problems (no luck there, either... yet)
    I'm a bit curious how/why the system works with two interfaces in the same subnet.
    (Does it work if only one interface is active?)

    ...but just can't get out (ping 192.168.4.100/192.168.8.100/8.8.8.8/etc).
    BTW, you're aware that /etc/resolv.config shows nameservers at 194.168.X.100?
    Last edited by Iowan; December 28th, 2013 at 04:56 AM.
    Linux User #415691 Ubuntu User #8629
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  3. #3
    Join Date
    Oct 2005
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    Re: Network connected but no internet connection

    Thanks for the reply. The network cards simply grab an IP each - from what I understand, as long as they each have a separate IP & MAC they should work together side by side (internal ethernet & external wireless dongle). No real need for it - it's a historical setup where I was moving the machine around from close to the router to far away. I've tried disabling the ethernet & trying with just the wireless but no luck. It's slightly tricky swapping between the two as it's a headless box in my loft with no other monitor in the loft, so I'm just hoping it all comes back online, but do far I've been able to disable, restart the network-manager, etc., and I can get back in again. I haven't tried static IPs which might be worth a shot.

    I hadn't spotted the nameserver typo, but just tried 194.168.X.100 without any luck. I've also looked at the longs on my router and can't see anything from the ubuntu box, so looks like it's not reaching it at all, rather than being rejected by it.

    Interestingly, when I try ping I get the following:
    Code:
    PING 194.168.4.100 (194.168.4.100) 56(84) bytes of data.
    From 192.168.1.109 icmp_seq=1 Destination Port Unreachable
    From 192.168.1.109 icmp_seq=2 Destination Port Unreachable
    From 192.168.1.109 icmp_seq=3 Destination Port Unreachable
    Where it says Destination PORT Unreachable, I was expecting HOST, although this might just be my Windows experience coming through....

    EDIT: FYI, I can SSH into either IP address without enabling/disabling
    Last edited by Tass; December 28th, 2013 at 02:09 PM. Reason: update

  4. #4
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    Re: Network connected but no internet connection

    From http://support.microsoft.com/kb/325122:
    Port Unreachable - generated if the designated transport protocol (e.g., UDP) is unable to demultiplex the datagram in the transport layer of the final destination but has no protocol mechanism to inform the sender;
    Similar information here... bouncing off my skull this morning.
    ... might see if Network Tools>Traceroute reveals anything useful.
    Last edited by Iowan; December 28th, 2013 at 02:56 PM.
    Linux User #415691 Ubuntu User #8629
    Iowa Team (LoCo): [Wiki] [Launchpad] [Sub-forum]
    IRC channel: #ubuntu-us-ia on irc.freenode.net

  5. #5
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    Re: Network connected but no internet connection

    Useful in that it's starting to isolate the issue - it's firmly in the OS network stack it seems. There's only 1 entry in traceroute, hostname = 192.168.1.109, IP = 192.168.1.109, time = 0.652. It's hitting it's local address and dying there...

  6. #6
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    Oct 2005
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    Re: Network connected but no internet connection

    Interestingly....

    I can ping other machines on my network (192.168.1.120) from the Ubuntu machines, but if I try run traceroute I get the same result - just a single entry listing the local IP (192.168.1.109).

  7. #7
    Join Date
    Oct 2005
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    Re: Network connected but no internet connection

    So here's an interesting test - connected the ubuntu machine to my mobile phone AP, connect my laptop to the same AP, connect to the ubuntu machine - almost the same issue. This time I could point the gateway (my phone in this case - 192.168.43.1), but couldn't ping anything external. From my laptop, connected to the same phone, I could ping both the router and anything external.

    I'm not sure if being able to ping the gateway on the mobile AP but not on the wlan0 or eth0, but the end result is same - can't get out. Now that I can reach the "router" I've looked at the tracepath results, which reveal a little more:
    Code:
    tass@springfield:~$ tracepath 192.168.43.1
     1:  springfield                                           0.169ms pmtu 1500
     1:  192.168.43.1                                          2.544ms reached
     1:  192.168.43.1                                          2.728ms reached
         Resume: pmtu 1500 hops 1 back 64
    tass@springfield:~$ tracepath 192.168.43.190
     1:  springfield                                           0.168ms pmtu 1500
     1:  ukcrdev19                                             2.903ms reached
     1:  ukcrdev19                                             2.783ms reached
         Resume: pmtu 1500 hops 1 back 128
    tass@springfield:~$ tracepath 173.194.70.102
     1:  springfield                                           0.249ms reached
         Resume: pmtu 65535 hops 1 back 64
    You'll notice that when I run tracepath against the "router" or my laptop, I get an actual trace with the relevant hops, but when I run it against 173.194.70.102 (google.com, pingable from my laptop on the same network), it doesn't leave the ubuntu machine, completing instantly.

    Here's my latest routing table - looks fine from what I can tell, nice and simple:
    Code:
    tass@springfield:~$ route -n
    Kernel IP routing table
    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    0.0.0.0         192.168.43.1    0.0.0.0         UG    0      0        0 wlan0
    192.168.43.0    0.0.0.0         255.255.255.0   U     2      0        0 wlan0
    I've also tried to rebuild my resolv.conf file (sudp dpkg-reconfigure resolvconf) with the same results.

    Here's my /etc/resolv.conf - I presume it doesn't have any other nameservers and my mobile provider doesn't push this down?
    Code:
    # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
    #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
    nameserver 127.0.0.1
    I can't reinstall network-manager without a connection as far as I can tell. Not sure if there are any other ways to do this offline? I might need to drag this box out of my loft though - I'm starting to think a full reinstall might just be easier here...

  8. #8
    Join Date
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    Re: Network connected but no internet connection

    You could enter the information into /etc/network/interfaces - or try a static address and manual DNS/routing information.
    I'm not sure that's the best route (pardon the pun), but it's something to try...

    There are a couple of similar threads. I'm anxious to see a solution - especially if the threads share a similar solution.
    Linux User #415691 Ubuntu User #8629
    Iowa Team (LoCo): [Wiki] [Launchpad] [Sub-forum]
    IRC channel: #ubuntu-us-ia on irc.freenode.net

  9. #9
    Join Date
    Oct 2005
    Beans
    38

    Re: Network connected but no internet connection

    OK - thanks. I'll give that a go. I'm now back on my main router with just eth0 connected, with a static IP and manual DNS (194.168.4.100, 194.168.8.100) and I can now at least ping my router which I couldn't before. tracepath has changed it's behavior too now, but it's displaying a no reply message now for some reason:
    Code:
    tass@springfield:~$ tracepath 192.168.1.1
     1:  192.168.1.201                                         0.178ms pmtu 1492
     1:  no reply
     2:  no reply
     3:  no reply
    I've been trying a few of the suggestions on the other threads, but no luck yet.

  10. #10
    Join Date
    Apr 2012
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    5,158

    Re: Network connected but no internet connection

    oops - scratch that, I see your eth0 MTU is set to 1492 already

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