[SATLUG] ifconfig commands

Geoff geoff at w5omr.shacknet.nu
Fri Apr 18 01:12:47 CDT 2008

Here's a headscratcher (for me, anyway)

yesterday, sometime between 2am and 6:30am, TW/RR issued a new ip 
address.  Took a while to figure out what was happening... all kinds of 
bad scenarios were going through my mind... cable modem gone bad... nic 
bit the dust, 10/100 switch finally crapped out after 7 years... etc...

so, I unplugged the cable modem from eth0 on the openSuSE 10.3 server, 
and plugged it into the slaptop, running winders.  Bam!  had 
connection.   Hmmm...

ok - not the cable modem, but that don't clear eth0 or the switch...

got to dinking on the command line....

'ifconfig eth0'
resulted in the same ip I've had for better'n 8 months...

I thought 'well, let's release and renew and see what happens'.

Unplugged the cable modem again and plugged it back in.  Ran
'ifconfig eth0 down'

then did

'ifconfig eth0'

and immediately had a different ip address *and* internet connection.

Uhm... 'ifconfig eth0 down' I understand doesn't unload the module or 
unconfigure it, just places the the interface called eth0 in a downed 

but... (and here's where I'm scratching my head) if I ran 'ifconfig eth0 
down' and then did 'ifconfig eth0' and had a different ip address, and 
connectivity with the outside world, why didn't I have to 'ifconfig eth0 
up' ?


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