[Linux-disciples] Resolv.conf, straw, etc.

[Adam Rosi-Kessel]

ifup brings the interface up and then runs dhclient. Joining the
rosi-kessel WLAN, as I understand it, is a totally separate layer from
the dhclient. Normally as you move between access points, the card should
dissociate itself and reassociate itself--if you look at dmesg you'll see
messages to that effect. But sometimes I've found I need to do iwconfig
[interface name] essid any to get it to "reset" and look for a new access
point.

But: associating with a new access point generally won't automatically
run dhclient and fetch a new IP address. So you usually need to do
ifdown/ifup or at least dhclient to get the new IP and DNS.

But, yeah, the rosi-kessel router *should* be giving you a new DNS for
/etc/resolv.conf when you ifup and dhclient asks for that information.
Your assigned IP address, your netmask, your gateway, and your DNS are
all handed out by the router.  This is totally unrelated to the WiFi
part--it works the same way with an ethernet router.

On Thu, Dec 30, 2004 at 08:14:26AM -0500, Stephen R Laniel wrote:
> On Wed, Dec 29, 2004 at 03:19:50PM -0500, Adam Rosi-Kessel wrote:
> > Usually you don't have to worry about any of this--you do ifup in your
> > current environment, and the correct nameserver IP is inserted into
> > /etc/resolv.conf by dhclient.  I'm not sure why that doesn't just work
> > for you.
> Hm. When my wireless card (via iwconfig) reports that its
> new ESSID is, say, 'rosi-kessel', did it get that ESSID by
> ifuping within range of 'rosi-kessel'? Because what seems to
> be happening is that my laptop is retaining the old
> nameservers inside of resolv.conf -- the nameservers given
> by a different router with a different ESSID -- and, I
> think, keeping their names before the names of 'rosi-kessel'
> nameservers. I suspect that this is causing strange timeouts
> because, say, my laptop tries to look up names within the
> other nameserver, can't find it, and falls back to the
> 'rosi-kessel' nameserver. Some applications will wait for
> this whole process to happen; some won't.
> 
>  From what you say, I gather that resolv.conf should lose
> its old nameservers and gain new ones when switching between
> routers, and should do so automatically. It should do this,
> I would think, without my having to manually ifdown/ifup.
> Isn't that so?
-- 
Adam Rosi-Kessel
http://adam.rosi-kessel.org
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