Using Ubuntu Server (12.04) via command line, I can access the LAN (e.g. ping local machines) but not the internet (e.g. "ping google.com" or "sudo apt-get update"). How should I troubleshoot this?
I'll start by saying that I was able to access the internet (using sudo apt-get) but after some 'configuration work' I can now only access the LAN. It previously worked when I had a DHCP connection. I noticed the problem some time after I'd switched to a static IP. I've switched back to DHCP but with no luck.
/etc/network/interfaces currently looks like this:
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp
auto wlan0
iface wlan0 inet dhcp
wpa-ssid myrouterssid
wpa-psk myrouterpassword
ifconfig -a reports:
eth0 Link encap:Ethernet HWaddr 00:1e:7a:d9:1b:07
inet addr:192.168.0.101 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::21e:68ff:fed9:1b07/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:217 errors:0 dropped:0 overruns:0 frame:0
TX packets:414 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:23826 (23.8 KB) TX bytes:47487 (47.4 KB)
Interrupt:16
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:12 errors:0 dropped:0 overruns:0 frame:0
TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:720 (720.0 B) TX bytes:720 (720.0 B)
virbr0 Link encap:Ethernet HWaddr 86:19:a7:9b:a6:4a
inet addr:192.168.122.1 Bcast:192.168.122.255 Mask:255.255.255.0
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:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
wlan0 Link encap:Ethernet HWaddr 00:94:ea:de:1f:78
inet addr:192.168.0.3 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::216:eaff:fede:1f78/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:328 errors:0 dropped:0 overruns:0 frame:0
TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:58008 (58.0 KB) TX bytes:1852 (1.8 KB)
"ping 192.168.0.1" (gateway) works. "ping 192.168.0.100" (self) works. "ping 192.168.0.7" (another PC) works. "ping google.com" reports "ping: unknown host google.com". "ping 173.194.34.72" (google.com) fails.
I can also SSH to this ubuntu server from another PC (although it now waits about 20 seconds before it asks for the password whereas it was previously instantaneous – significant?)
EDIT: route -n reports:
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.0.1 0.0.0.0 UG 100 0 0 eth0
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 wlan0
192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0
Best Answer
Your resolv.conf entries are probably bad. You should determine the proper address(es) and write them manually in resolv.conf (removing current entries).
I guess that DNS server is the same as gateway (192.168.0.1).
You can try this before making changes in resolv.conf by command:
Above command tries to ask 192.168.0.1 (not Your current set in resolv.conf) for google.com IP, if there is working DNS server the answer will contain following text:
If it fails try entering different IPs in
digcommandAnother problem is that trying to ping google by IP fails (as you wrote). To make a quick test why it fails try following command:
You'll see which one of the hops causes the problem. It's possible that Your gateway is not working.