udev won't let me change my network interface?

["C. G. Montgomery" <cgm@physics.utoledo.edu>]

I have a desktop computer running Debian testing (squeeze),  kernel 
2.6.30, with KDE 4.2.4. Previously it had been connected by ethernet to a 
similar machine using an interface eth0.  Now I want to connect it to my
new DSL service.

I changed /etc/network/interfaces to contain:

# /etc/network/interfaces -- configuration file for ifup(8), ifdown(8)

# The loopback interface
auto lo
iface lo inet loopback

# for DSL
iface eth1 inet dhcp

and rebooted the machine.  Then I have 

offnode2:/home/cgm# ifconfig -a
eth0      Link encap:Ethernet  HWaddr 00:c0:26:6c:40:fc
          inet6 addr: fe80::2c0:26ff:fe6c:40fc/64 Scope:Link
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          collisions:0 txqueuelen:1000
          RX bytes:32896 (32.1 KiB)  TX bytes:3063 (2.9 KiB)
          Interrupt:9 Base address:0x2000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:268 errors:0 dropped:0 overruns:0 frame:0
          TX packets:268 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:23236 (22.6 KiB)  TX bytes:23236 (22.6 KiB)

The old eth0 interface is there, not the new eth1. I suspect udev is 
interfering somehow. 

ifup eth1 has no visible effect.  ifup eth0 reports:
Ignoring unknown interface eth0=eth0.

I can find discussions of how to change the name of an existing interface
with udev, but nothing about removing one interface and adding another. 
Any suggestions welcome.  Let me know if other information would be
useful.

regards   cgm