Question

2

No network connection but nameserver ok, no firewall

rated 0 times [ 2] [ 0] / answers: 1 / hits: 406 / 3 Years ago, sat, july 24, 2021, 5:28:47

for two days, my laptop cannot connect to the internet (a.k.a. all machines beyond my router) anymore. I have investigated the following things:

The network access worked fine half a week ago.

I have no idea, what could have caused the outage.

System: Ubuntu 14.04, XFCE, fully patched

I can access just fine the router's web interface and even other machines in my home net

I cannot reach any server outside, neither by name nor by IP.

I added Google's 8.8.8.8 as DNS resolver, no change (no surprise after finding 5...)

ufw is disabled:

$ sudo ufw status

WARN: Doppeltes Profil 'Apache', zuletzt gefundenes wird verwendet

WARN: Doppeltes Profil 'Apache Secure', zuletzt gefundenes wird verwendet

WARN: Doppeltes Profil 'Apache Full', zuletzt gefundenes wird verwendet

Status: Inaktiv

iptables have no strange entries:

$ sudo iptables-save

*filter

:INPUT ACCEPT [240:30526]

:FORWARD ACCEPT [0:0]

:OUTPUT ACCEPT [2994769:4696400653]

COMMIT

I checked with the router, there is no active firewall there. Also all other computers, each running Ubuntu, can connect to the net just fine.

There's no difference between eth0 and wlan0, both do not work.

ifconfig output:

$ ifconfig

eth0      Link encap:Ethernet  HWaddr 00:17:a4:e8:2a:9c  

          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:18 



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:65536  Metric:1

          RX packets:229 errors:0 dropped:0 overruns:0 frame:0

          TX packets:229 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:0 

          RX bytes:30871 (30.8 KB)  TX bytes:30871 (30.8 KB)



tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  

          inet addr:10.8.0.6  P-t-P:10.8.0.5  Mask:255.255.255.255

          UP POINTOPOINT RUNNING NOARP 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:100 

          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)



wlan0     Link encap:Ethernet  HWaddr 00:1b:77:34:2f:09  

          inet addr:192.168.178.23  Bcast:192.168.178.255  Mask:255.255.255.0

          inet6 addr: fe80::21b:77ff:fe34:2f09/64 Scope:Link

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

          RX packets:188 errors:0 dropped:0 overruns:0 frame:0

          TX packets:262 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000 

          RX bytes:27175 (27.1 KB)  TX bytes:35542 (35.5 KB)

Output of route -n:

$ route -n

Kernel IP routing table

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

0.0.0.0         10.8.0.5        128.0.0.0       UG    0      0        0 tun0

0.0.0.0         192.168.178.1   0.0.0.0         UG    0      0        0 wlan0

10.0.0.0        10.8.0.5        255.255.255.0   UG    0      0        0 tun0

10.8.0.1        10.8.0.5        255.255.255.255 UGH   0      0        0 tun0

10.8.0.5        0.0.0.0         255.255.255.255 UH    0      0        0 tun0

128.0.0.0       10.8.0.5        128.0.0.0       UG    0      0        0 tun0

188.192.138.205 192.168.178.1   255.255.255.255 UGH   0      0        0 wlan0

192.168.178.0   0.0.0.0         255.255.255.0   U     9      0        0 wlan0

I am basically at my wits' end now. What can I try to bring the laptop back to connecting to the 'Net? Any diagnosis data that you need will be given with pleasure.

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ledeball

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3 Years ago

answered 3 Years ago huovie · Accepted Answer

Try this:

# stop network manager

sudo /etc/init.d/NetworkManager stop

# if on a cable connection, re-run with dhcp

sudo ip link set dev eth0 down

sudo dhclient eth0

# try to ping via ip first

ping 8.8.8.8

(Update after ifconfig output)

Currently you use wlan, just to make sure plug in a caple and re-check with eth0 and DHCP. There must be a default route to the gateway as was noted in a comment, e.g.

 sudo ip route add default via 192.168.178.1