[PLUG] Network issues

[Mike Connors]

drew wymore wrote:
> Would love to try what you suggest, except I do not understand.  Is
> this something that I can do when the network is in the failed state?
Okay, so let me see if I got this straight? Networking only fails upon 
bootup and when it doesn't work you can't ping the router and you don't 
see an entry "1000baseT/Full"under "Advertised link modes"?

Okay, so lets start from OSI layer 1 and work up.

1. When networking fails upon bootup are there lights on your ethernet 
ports on the computer and on the router?

2. When you run the command "ifconfig -a", is the eth interface listed? 
Does it have an ip addr?

3A. If the eth interface is listed, what happens if you attempt to 
manually bring up the eth interface with "ifup eth#" command.

Does it say it's already configured?

root at mc-goose:~# "ifup eth2"
ifup: interface eth2 already configured

Or does is say throw an error?

3B.  If the eth interface is *not* listed, what happens if you grep 
dmesg for that interface, such as:

root at mc-goose:~# "dmesg | grep eth0"

0000:02:00.0: eth0: (PCI Express:2.5GB/s:Width x1) 00:15:58:82:11:2e
0000:02:00.0: eth0: Intel(R) PRO/1000 Network Connection
0000:02:00.0: eth0: MAC: 2, PHY: 2, PBA No: 005301-003

With mii-tool and ethtool you can change default settings of network 
interfaces for such things as enabling/disabling auto-negotiation and/or 
forcing the speed/duplex.

What I've discovered with auto-negotiation is the same with other 
standards, not everyone interprets or implements them the same. If you 
have Intel or 3COM NICs on both ends auto-neg works flawlessly. You get 
two different vendors on each end, especially if they're consumer level 
products and it's pretty much a crap shoot.