Re: [probably OT] how to switch between wired and wireless

John Haxby <jch@xxxxxxxxxxxxxxxxxx> · Fri, 06 Jun 2003 09:54:53 +0100

I have a similar set up here, well, not here, at home.   It's slightly 
complex.  I use DHCP to assign a fixed IP address no matter what 
interface I'm using.   If I want to switch from one interface to another 
manually I do "ifdown ethN; ifup ethM" (N and M being 0 and 1, but not 
necessarily in that order).   Mostly I don't need to do that since I 
either have wireless or wired available but not both.   Since I keep the 
same IP address, I can even maintain a TCP connection while I'm swapping 
hardware -- it looks odd, but it works.  Well, it did the one time I've 
actually done that.   It's great there was a file transfer pootling 
along at, oh, perhaps as much as a megabyte a second and then it 
suddenly shot up to 9 meg a second when I plugged the wired connection in.

In the office, I have a different IP address and that's hardwired to the 
same two MAC addresses.   There's a slight problem in moving from home 
to work and vice versa -- applications tend to read /etc/resolv.conf 
when they start up and use that to decide which name server to talk 
to.   Unfortunately, the name server at home isn't reachable from work 
and the name server at work doesn't do recursive queries from outside 
(and doesn't know about the private network at home).   The upshot of 
that is that I have to restart some applications (e.g. mozilla, 
rhn-applet-gui, nfs server) when I go from work to home or back again, 
and sometimes there's enough confusion that it's easier to reboot.

Chris Rouch wrote:

I've just installed a wireless lan card on my laptop (compaq armada M700
running red hat 9). I've set up both interfaces to not start on boot and
to so I can start and stop them as a normal user. So after booting,

ifup eth1 will fire up the wireless link. This works well. The problem
comes if I want to move from wireless to wired or vice versa (e.g if I
move to another part of my apartment where the wireless signal doesn't
reach). In that case, any applications connect over the other lan
connection will hang. The only clean way to switch networks is to
reboot.

I'm using dhcp to get ip addresses, and assigning different ip addresses
to the two lan interfaces.

So, my questions:

How do other people deal with this?
Is giving both interfaces the same ip address a bad thing?
Would it help anyway?

I'd appreciate any help with this.

Thanks and regards,

Chris Rouch

PS This setup (orinico gold card, linksys access point) worked with very
little effort under red hat 9. Just a few minutes configuring the access
point and then everything just worked.