ubuntu eth0 not reconnecting after cable unplugged

Question

I'm running kubuntu 9.10 w/ gnome, I have a static IP defined in /etc/network/interfaces

When I unplugged my network cable and rebooted, then reconnected the network cable I was not able to connect. I tried using sudo ifup eth0, and then ifconfig and it seemed as though the IP address had been assigned and I was connected, but I wasn't. I then did ifdown eth0, and again ifup eth0. For some reason I'm not able to access the network. Furthermore, I also attempted to connect via wlan, and was able to connect to the wireless network, but cannot "see" the network. I can't transfer data or access the internet or anything on the network including the router.

How do I resolve this?

topsy@monolyth:~$ ifconfig
eth0      Link encap:Ethernet  HWaddr 00:1c:25:1c:df:70  
          inet addr:192.168.1.145  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::21c:25ff:fe1c:df70/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5720 errors:0 dropped:0 overruns:0 frame:0
          TX packets:565 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100 
          RX bytes:378035 (378.0 KB)  TX bytes:46832 (46.8 KB)
          Memory:fe000000-fe020000 

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:4 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:240 (240.0 B)  TX bytes:240 (240.0 B)

By access the network I mean the local network as well as the internet.

topsy@monolyth:~$ ping 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=9.14 ms
64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=1.24 ms
64 bytes from 192.168.1.1: icmp_seq=3 ttl=64 time=1.01 ms
64 bytes from 192.168.1.1: icmp_seq=4 ttl=64 time=1.00 ms
[snip... all OK, icmp_seq from 5-30, time between 0.981-1.25ms]
^C
--- 192.168.1.1 ping statistics ---
30 packets transmitted, 30 received, 0% packet loss, time 29035ms
rtt min/avg/max/mdev = 0.971/1.300/9.140/1.458 ms

topsy@monolyth:~$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     *               255.255.255.0   U     0      0        0 eth0
link-local      *               255.255.0.0     U     1000   0        0 eth0
default         192.168.1.1     0.0.0.0         UG    100    0        0 eth0

root@monolyth:~# cat /etc/resolv.conf
# Generated by NetworkManager

Solution

Try this:

> sudo /etc/init.d/networking restart

If this does not help, check that the cable is "really" plugged - i.e. do the lights on the interface and on the switch/router are lit on.

Please, also, post as part of the question the output of these commands:

> ifconfig

> ping 192.168.1.1

> cat /etc/resolv.conf

> route

Comments

[quack quixote]

the ping output shows you are accessing the local network; what exactly isn't working?

[Alex]

I have tried your suggestion, but to no avail. I added my ifconfig. The network lights both on the laptop and the router for that network cable are on.

[Sunny]

Can you ping 192.168.1.145? Oh, and btw, pls edit your answer once more, unfortunately I don't have enough rep to do it. Mark all the ipconfig output, and click on the smal icon with 1s and 0s above the edit window. this will mark it as "code", and will format it properly for display. Before saving the edit, check the output, so you see how it looks. Cheers.

[Sunny]

I also added in my answer some more commands for you to show the output. Looks like the interface itself is working, so the problem should be either DNS, or routing. Pls, also define "access the network" - the local network, or Internet.

[Alex]

I have added the information you requested.

[Sunny]

From what you post, you can access local network. So, pls, re-phrase your q. to tell us what exactly is not working.

[Alex]

I cannot access any network shares, any computers on the network, the internet, basically anything that involves networking. This is the same for my file manager, browser, instant messenger, package manager etc. I have temporarily resolved the problem by editing my /etc/network/interfaces to remove the lines specifying a manual ip, subnet, and gateway and rebooted, however the problem returns if I add those lines again and unplug my network cable.