[wplug] static DHCP via multiple interfaces

[Patrick Wagstrom]

I've got a Thinkpad t43p laptop that has both wireless and wired 
interfaces.  The wireless is an intel a/b/g that runs using the madwifi 
driver.  Unfortunately, somewhere along the process of development of 
Ubuntu Edgy (Oct 2006), they mangled the driver and it has a performance 
regression from Dapper (Jun 2006). (For more information on the issue 
see https://bugs.launchpad.net/ubuntu/+source/linux-meta/+bug/63886)

This has led me to utilize both the wireless and wired interfaces.  I 
use the wired connection when I'm working on my desk at home, and the 
wireless when I'm elsewhere, such as "working" from the couch.  On my 
network IP address allocation is handled by a WRT54GL that's running 
DD-WRT 23sp2.  Both interfaces are entered into the static DHCP address 
table on the WRT54G.

Right now these addresses are different from one another.  This means 
that when I switch from the wireless to the wired interface all of my 
previous sessions, such as remote X sessions to work or NFS connections 
break.  Suckage.  This leads me to take a few minutes to restart from 
where I was.  When I was in Boston at the GNOME Summit last year, one of 
the folks there mentioned that on their network they had it configured 
so their wired and wireless laptop interfaces will get the same IP 
address.  NetworkManager then switches the networks and the connections 
- ssh, nfs, etc - all continue to work.

 From what I understand about IP and TCP this should be possible, as the 
OS will still know the proper sequence numbers to send for the 
connections, indicating that the connection can continue.  Anecdotally, 
it seems this works as when the wifi interface dies and comes back 
shortly afterward, my ssh sessions usually persist.  Anyway, before I go 
deeper into the problem, I just wanted to make sure my interpretation 
was correct and that it is the case that I can switch interfaces and if 
they have the same IP address my TCP connections will work.

Secondly, is it possible to do this with DD-WRT?  DD-WRT has a web gui 
for configuration and if I try to enter a static IP that is already 
assigned I'll get an error message saying it's already assigned.  Is 
this a situation where I need to modify settings in the nvram directly?

Anyway, thanks for reading.  Help is appreciated.

--Patrick