Checklist: Ethernet Problems

Message

mdeininger · Post by **mdeininger** » Thu Aug 17, 2006 7:42 pm

as wynn pointed out in this thread we really could use a checklist for network problems, since lots of threads on this are spawning just now, so here goes:

Before asking for help on your Ethernet Setup, check the following:

are the right modules loaded? using
Code: Select all
```
lspci
```
can often help you determine which modules you need.
did you try to use the net-setup command?
are you sure your ethernet is eth0? remember that you can always list all your network devices using
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```
ifconfig -s -a
```
. be sure to try all of the eth* devices with net-setup.
does
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```
mii-tool
```
have anything useful to say about the link status of your ethernet devices?
did you try to manually configure your network?
are there any suspicious/fishy error messages on the console when loading the proper module or in dmesg? check with
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```
dmesg
```
are your routes (i.e. what gateway to use) set up properly? check with
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```
route -n
```
is dns resolution set up properly? check with
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```
cat /etc/resolv.conf
```
does it work while installing, but not after booting? check your kernel configuration.

More things to read before panicking:
there's lots of nifty resouces to be found on these forums...

What exactly doesn't work?
Network errors can have lots of causes, so you should formulate your issue very precisely. "it doesn't work" doesn't really help anyone in trying to figure out what's wrong.

has your interface been assigned an IP address, either manually or via DHCP? check with
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```
ifconfig
```
can you ping an IP address on your LAN? for example:
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```
ping 192.168.0.1
```
can you ping an internet IP address? for example:
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```
ping 66.249.85.104
```
(one of google's IP addresses)
can you ping an internet hostname? for example:
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```
ping www.google.com
```
can you browse to a website? for example:
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```
links2 www.google.com
```
or try a browser on the livecd
if it doesn't work inside your chroot, does it work outside of it? if so, did you copy the cd's /etc/resolv.conf into your installation's /etc directory?
post-installation: did it work on the livecd, but now it doesn't anymore? you most certainly lack some modules/kernel options then.

Additional information that could help us help you
if you have network problems, please try to provide as many of the following so we can figure out what's wrong:

any relevant sections of lspci:
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```
lspci|grep Network
```
(or similarly with lsusb for USB devices)
any relevant info in dmesg:
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```
dmesg|grep -i eth
```
the output of
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```
lsmod
```
the output of
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```
ifconfig -a
```
the output of
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```
route -n
```
in really tough cases, this could also help: the output of
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```
gzcat /proc/config.gz|grep -i NET
```

i hope this checklist will be useful. could a moderator make this sticky, please? i feel this could come in handy... if anyone has anything to add, just post here and i'll add it to the list [i'm sure i forgot a lot

]

wynn · Post by **wynn** » Thu Aug 17, 2006 8:15 pm

There's also NeddySeagoons' Rough guide to Fixing Networking which I've only just remembered.

He goes into how to find the correct module/driver (Sieve of NeddySeagoon?) and mentions the firewire eth1394 problem which has bitten almost everyone.

mdeininger · Post by **mdeininger** » Thu Aug 17, 2006 8:24 pm

yep, the eth1394 really is a popular one. and really confusing at that since nobody would expect a firewire port to be listed as an ethernet device... not at first, anyway. just added the link

wynn · Post by **wynn** » Tue Aug 22, 2006 3:06 pm

One other comment: do you think putting

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route -n

instead of just

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route

would help?

If DNS isn't working, just plain "route" can take some time and (thinks back) the timid might think it's broken.

Otherwise it's brilliant. There just can't be any more "my networking is broken" posts

mdeininger · Post by **mdeininger** » Tue Aug 22, 2006 6:40 pm

heh, thanks wynn, you're perfectly right. i'll edit it right away

i sure hope this covers most of the problems and gets enough attention,... maybe we should do the same for the good ol' vfs errors

wynn · Post by **wynn** » Tue Aug 22, 2006 7:04 pm

maybe we should do the same for the good ol' vfs errors

(runs QuickSearch) Oh, you mean

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Kernel panic - not syncing: VFS: Unable to mount root fs on unknown block (0,0)

The omens are not good, quote from LWN taken from LKML

The current -mm tree is 2.6.18-rc4-mm1. Recent changes to -mm include a reworking of the serial ATA configuration options ("If you blindly run `make oldconfig' you won't have any disks."),

But it would be nice to collect all the wisdom in these forums which has been showered on the problem. I bet NeddySeagoon has a Rough Guide, yes, partly, his "Rough Guide to DIY Kernels" http://forums.gentoo.org/viewtopic-p-24 ... ml#2431534 "roughly" (tm) covers the issues.

mdeininger · Post by **mdeininger** » Tue Aug 22, 2006 8:01 pm

yep, exactly that type of errors. and someone should point out that the number in () is pretty important with this type of error message, because it gives people a rough clue about what's wrong. and someone ought to point out that device names can change between kernel versions *nods*.

i mean, i did see *lots* of posts with kernel panics due to badly configured kernels and similar things.