Network unreachable on eth0

[bkg]

I have a Mac OS X host and a bunch of guests including Ubuntu and Arch Linux. I was trying to set up a host-only network at eth1 to let me ssh into the system. But now eth0 isn't working properly either. Ubuntu can no longer connect to remote hosts or browse the internet. It tells me that the network is unreachable. Where should I start looking? I tried to grep some logs, but there was way too much detail and I don't have a systematic process for narrowing the possibilities down.

Here's the result of ifconfig:

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$ifconfig
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:10968 errors:0 dropped:0 overruns:0 frame:0
          TX packets:10968 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:897264 (897.2 KB)  TX bytes:897264 (897.2 KB)

Other diagnostic commands and the output:

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$sudo lspci -n
00:00.0 0600: 8086:1237 (rev 02)
00:01.0 0601: 8086:7000
00:01.1 0101: 8086:7111 (rev 01)
00:02.0 0300: 80ee:beef
00:03.0 0200: 8086:100e (rev 02)
00:04.0 0880: 80ee:cafe
00:05.0 0401: 8086:2415 (rev 01)
00:06.0 0c03: 106b:003f
00:07.0 0680: 8086:7113 (rev 08)
00:0d.0 0106: 8086:2829 (rev 02)

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$sudo lshw -c network                                                                                                      
  *-network DISABLED      
       description: Ethernet interface
       product: 82540EM Gigabit Ethernet Controller
       vendor: Intel Corporation
       physical id: 3
       bus info: pci@0000:00:03.0
       logical name: eth0
       version: 02
       serial: 08:00:27:7d:22:df
       size: 1Gbit/s
       capacity: 1Gbit/s
       width: 32 bits
       clock: 66MHz
       capabilities: pm pcix bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=e1000 driverversion=7.3.21-k8-NAPI duplex=full firmware=N/A latency=64 link=no mingnt=255 multicast=yes port=twisted pair speed=1Gbit/s
       resources: irq:19 memory:f0000000-f001ffff ioport:d010(size=8)

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$lsmod 
Module                  Size  Used by
nls_utf8               12557  1 
isofs                  40257  1 
vboxsf                 43743  2 
vesafb                 13844  1 
snd_intel8x0           38570  2 
snd_ac97_codec        134869  1 snd_intel8x0
ac97_bus               12730  1 snd_ac97_codec
snd_pcm                97275  2 snd_intel8x0,snd_ac97_codec
snd_seq_midi           13324  0 
snd_rawmidi            30748  1 snd_seq_midi
snd_seq_midi_event     14899  1 snd_seq_midi
rfcomm                 47604  0 
snd_seq                61929  2 snd_seq_midi,snd_seq_midi_event
bnep                   18281  2 
bluetooth             180113  10 rfcomm,bnep
ppdev                  17113  0 
psmouse                97519  0 
snd_timer              29990  2 snd_pcm,snd_seq
joydev                 17693  0 
snd_seq_device         14540  3 snd_seq_midi,snd_rawmidi,snd_seq
vboxvideo              12622  1 
serio_raw              13211  0 
snd                    79041  11 snd_intel8x0,snd_ac97_codec,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_seq_device
soundcore              15091  1 snd
vboxguest             235498  7 vboxsf
parport_pc             32866  0 
drm                   241971  2 vboxvideo
i2c_piix4              13301  0 
snd_page_alloc         18529  2 snd_intel8x0,snd_pcm
mac_hid                13253  0 
lp                     17799  0 
parport                46562  3 ppdev,parport_pc,lp
usbhid                 47238  0 
hid                    99636  1 usbhid
e1000                 108589  0

[socratis]

Where should I start looking? I tried to grep some logs, but there was way too much detail and I don't have a systematic process for narrowing the possibilities down.

You could definitely start here: Minimum information needed for assistance. Also in the Rules and FAQ and in the Howtos and Tutorials. I couldn't get any useful information from the logs that you provided.

[bkg]

Thanks for linking to the post describing the minimum useful information. Here it is.

Virtualbox version : 4.3
Guest Additions Installed? : Yes
Host: Mac OS X 10.9 64 bit
Guest: Ubuntu 12.04 LTS 64 bit
Logs & Additional Info: Attached

[bkg]

I eventually solved the problem. The fact that the same network interface eth0 wasn't working in two different guest operating systems was the clue. The easiest way to get the interface to work again was to do the following sequence of steps:

• Remove the persistent rules for naming the network interfaces when the networking service starts (/etc/udev/rules.d/*net-rules for Ubuntu)
  Restore default settings for the network interface configuration file (/etc/network/interfaces for Ubuntu)
  Restart the networking service (/etc/init.d/networking restart)

This article pointed me in the right direction.