Can't access internet (DNS problem?)

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Can't access internet (DNS problem?)

Postby Zewz on Fri Dec 06, 2013 8:16 am

Hello everyone!

I've use Mint for over two years now and I'm really happy with it and this community - I've learned a lot through it! But now I can't figure out whats wrong, and I'd really like to understand it/fix it!

Background:
I'm running Maya on a HP elitebook, but the wireless has always worked flawlessly so I am inclined to think it's some settings I messed up manually or or through some update. Wired networking works fine, right now I'm writing this from an 3G connection through my phone (working out of the box, way easier than under windows - impressive!)

The problem:
The internet connection is very unreliable. Most often I'll connect successfully to the wireless network at home, can access the router and can ping "8.8.8.8" but not "google.com". Then after some time I suddenly can get online and the ping to google.com unexpectedly is successfull. I have automatic DHCP, but tried to fiddle around with it manually without results.

The problem is that the problem almost seems random in that it doesn't always appear.

Thesame goes for the universitys eduroam, most often I cannot get online, but sometimes it works and then it works for a long time.

Trubleshooting:
Here is what i've done so far and what I can think of.

Output from mintwifi:
Code: Select all
-------------------------
* I. scanning WIFI PCI devices...
  -- Intel Corporation PRO/Wireless 5100 AGN [Shiloh] Network Connection
      ==> PCI ID = 8086:4237
-------------------------
* II. querying ndiswrapper...
-------------------------
* III. querying iwconfig...
lo        no wireless extensions.

eth1      no wireless extensions.

wlan0     IEEE 802.11abgn  ESSID:"NETGEAR61" 
          Mode:Managed  Frequency:2.422 GHz  Access Point: 74:44:01:92:54:A4   
          Bit Rate=65 Mb/s   Tx-Power=15 dBm   
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=70/70  Signal level=-39 dBm 
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:29  Invalid misc:296   Missed beacon:0

eth0      no wireless extensions.

-------------------------
* IV. querying ifconfig...
eth0      Link encap:Ethernet  HWaddr 1c:c1:de:36:af:17 
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:22 Memory:d8800000-d8820000

eth1      Link encap:Ethernet  HWaddr 5e:95:ae:34:90:d7 
          inet addr:172.20.10.3  Bcast:172.20.10.15  Mask:255.255.255.240
          inet6 addr: fe80::5c95:aeff:fe34:90d7/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:144 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1407 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:22212 (22.2 KB)  TX bytes:165047 (165.0 KB)

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:5920 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5920 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:844917 (844.9 KB)  TX bytes:844917 (844.9 KB)

wlan0     Link encap:Ethernet  HWaddr 00:22:fa:cf:83:c4 
          inet addr:192.168.1.7  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::222:faff:fecf:83c4/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:364 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2791 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:80924 (80.9 KB)  TX bytes:379738 (379.7 KB)

-------------------------
* V. querying DHCP...
[sudo] password for zimon:
Rather than invoking init scripts through /etc/init.d, use the service(8)
utility, e.g. service smbd reload

Since the script you are attempting to invoke has been converted to an
Upstart job, you may also use the reload(8) utility, e.g. reload smbd
RTNETLINK answers: File exists
-------------------------
* VI. querying nslookup google.com...
Server:      172.20.10.1
Address:   172.20.10.1#53

Non-authoritative answer:
Name:   google.com
Address: 80.239.174.123
Name:   google.com
Address: 80.239.174.116
Name:   google.com
Address: 80.239.174.117
Name:   google.com
Address: 80.239.174.118
Name:   google.com
Address: 80.239.174.119
Name:   google.com
Address: 80.239.174.120
Name:   google.com
Address: 80.239.174.121
Name:   google.com
Address: 80.239.174.122


I checked what I successfully can ping:
127.0.0.1 - Successfull
192.168.1.1 - Successfull
8.8.8.8 - Sucessfull
google.com - Not sucessfull

I would post the outputs from iwconfig and ifconfig, but the connection just started to work, leaving me yet again clueless.

Questions:
- Is there a way to reset everything to the "original state"?
- Why can I ping 8.8.8.8 but not google.com?
- Has anyone seen this before and have an explanation or fix?
Zewz
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Joined: Fri Dec 06, 2013 7:32 am

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Re: Can't access internet (DNS problem?)

Postby wavespot on Fri Dec 06, 2013 11:33 am

Hi

Could you give us the content of /etc/resolv.conf file ? Also the output of 'route' command
wavespot
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Re: Can't access internet (DNS problem?)

Postby Zewz on Fri Dec 06, 2013 8:40 pm

I'll post the current output of the specified commands, but at the moment the internet works from the wireless. I don't understand why it works sometimes and some times it does not. When it doesn't work, even a complete reboot does not usually help.



Code: Select all
$ cat /etc/resolv.conf
nameserver 192.168.1.1

$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         192.168.1.1     0.0.0.0         UG    0      0        0 wlan0
link-local      *               255.255.0.0     U     1000   0        0 wlan0
192.168.1.0     *               255.255.255.0   U     2      0        0 wlan0

Zewz
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Re: Can't access internet (DNS problem?)

Postby wavespot on Mon Dec 09, 2013 4:51 am

yep, everything's fine here. Nevertheless, if you experiment again issue with DNS only (meaning every kind of ping works out, but google doesn't works in firefox saying Unknown host) then check around resolvconf.

Check /etc/resolv.conf
Debug tool : nslookup, or dig
wavespot
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Re: Can't access internet (DNS problem?)

Postby Zewz on Tue Dec 10, 2013 3:32 pm

But if there is a problem with the DNS, "ping google.com" should fail, while ping to any ip works, right?

How would I use the tools you mentioned?

I've had the problem on and off for maybe a month or so. The frequency of the problem has generally been low enough that I haven't cared much ("Internets down, rainbows. I'll do something else for the next few hours"). But it is really annoying, especially since I have no idea what it might be...
Zewz
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