Internet connection not working although it says it is connected

I have a Toshiba z830 with ubuntu 12.04. I could use without problems the DSL connection (I have no router, only a modem) at home until a couple of days ago:

It stopped to work when while connected with the DSL connection via CiscoVPN (to my workplace), I had to leave the laptop unattended for a while and I guess the laptop tried to go to suspend. When I came back there were many messages on a black screen (sorry, I cannot attach an image because of my low reputation) and the laptop was not responding. I had to reset the it.

After rebooting it, the internet connection didn't work as did before (no browsing, no ssh, no skype, etc) although it says it is connected. I only can browse, etc when I connect to CiscoVPN to the same place where I was connected when it crashed.

When I am physically where I connected via VPN (at work) I can use the wireless, which I am not able to use now anymore since the incident described above.

Some additional information:

martillu@ubuntu:~$ cat /etc/resolv.conf  
domain km.icrr.u-tokyo.ac.jp  
nameserver 10.240.12.134  
nameserver 10.240.12.135  

martillu@ubuntu:~$ route -n  
Kernel IP routing table  
Destination Gateway Genmask Flags Metric Ref Use Iface  
0.0.0.0 61.127.116.199 0.0.0.0 UG 0 0 0 ppp0  
61.127.116.199 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0  
169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 ppp0  

martillu@ubuntu:~$ ifconfig  
eth0 Link encap:Ethernet HWaddr e8:e0:b7:2f:bc:5a  
inet6 addr: fe80::eae0:b7ff:fe2f:bc5a/64 Scope:Link  
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1  
RX packets:17620 errors:0 dropped:1 overruns:0 frame:0  
TX packets:13168 errors:0 dropped:0 overruns:0 carrier:0  
collisions:0 txqueuelen:1000  
RX bytes:19452232 (19.4 MB) TX bytes:2568218 (2.5 MB)  
Interrupt:20 Memory:c0700000-c0720000  

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:134 errors:0 dropped:0 overruns:0 frame:0  
TX packets:134 errors:0 dropped:0 overruns:0 carrier:0  
collisions:0 txqueuelen:0  
RX bytes:36316 (36.3 KB) TX bytes:36316 (36.3 KB)  

ppp0 Link encapoint-to-Point Protocol  
inet addr:219.167.252.226 P-t-P:61.127.116.199 Mask:255.255.255.255  
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1454 Metric:1  
RX packets:17608 errors:0 dropped:0 overruns:0 frame:0  
TX packets:13129 errors:0 dropped:0 overruns:0 carrier:0  
collisions:0 txqueuelen:3  
RX bytes:18993590 (18.9 MB) TX bytes:2221195 (2.2 MB)  

wlan0 Link encap:Ethernet HWaddr 9c:b7:0d:d9:21:f3  
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)

I think that: domain km.icrr.u-tokyo.ac.jp in the resolv.conf may be suspicious, since if I am not connected via CiscoVPN I do not know why it should appear "km.icrr.u-tokyo.ac.jp" (this is where I connect via VPN).

Solution 1:

You are on the right track. the resolv.conf was changed for VPN use and was not changed back for normal use as a result of the crash. Deleting the old resolv.conf may help. You can make a backup copy of the file and delete the original with this single command:

sudo mv /etc/resolv.conf /etc/backup.resolv.conf

A new resolv.conf will be generated as and when needed. See the answer to the following question:

Can not access Internet (DNS names do not resolve) after update today

Also see:

http://www.stgraber.org/2012/02/24/dns-in-ubuntu-12-04/

Hope this helps.