how to get dhclient to reconfigure link?

David G. Miller dave at davenjudy.org
Thu May 3 14:06:10 UTC 2007


Alan Cox <alan at lxorguk.ukuu.org.uk> wrote:

> On Wed, 02 May 2007 22:46:06 -0400
> Joe Smith <jes at martnet.com> wrote:
>
>   
>> > I had to unplug my network connection (FC5; single PC-cable modem) for a 
>> > couple of hours today, and when I plugged it back in, the kernel 
>> > recognized that the link was up again, but the dhcp client did not 
>> > reconfigure the link. I tried ifconfig eth0 down/up--no change. I 
>> > finally just killed and re-started dhclient, which worked but seems 
>> > pretty clunky. What's the recommended solution?
>>     
>
> Either
>
> 	ifdown eth0
> 	ifup eth0
>
> (which will restart negotiation etc), waiting (which should eventually
> get around to retrying), or run the GUI network config tool and take the
> iface down/up.
It looks like dhclient will "stick" sometimes and not exit with an 
"ifdown".  I just had this happen this morning.  I've been working with 
and testing the wireless link on my laptop for about a week with lots of 
"ifdown eth0" (the wire) followed by "ifup eth1" (the wireless).  This 
morning I had to kill dhclient after the "ifdown eth0" before I could 
successfully do an "ifup eth1".  Maybe if your timing is perfectly wrong 
and you catch dhclient when it's getting a new lease or something it 
doesn't exit on an ifdown.

BTW, I finally got my wireless running stably on the laptop with 
ndiswrapper by going to the 2.6.21 kernel from kernel.org.  Really odd 
since I configured the kernel with "make oldconfig" and didn't see 
anything related to some of the known pitfalls for ndiswrapper (e.g., 
CONFIG_4KSTACKS) but it seems to run fine both over time (several days) 
and with lots of traffic (amanda backup keeps getting the rebuilt kernel 
files object files as I tweak the configuration).  This is with a x86_64 
kernel.

Cheers,
Dave

-- 
Politics, n. Strife of interests masquerading as a contest of principles.
-- Ambrose Bierce




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