thanks for the reply, but in this example there is already a second physical device peth1 which will
create then the second eth1 interface.
But what I want is an additional Virtual-Network interface which is not really there (physical).
I have one network card inside which will be mapped to peth0 and is build to the bridge (for example xenbr0)
For the Dom0 we are having then a eth0 Interface.
Now I want to create the veth1 which is bound for example to xenbr1. But this veth1 is not physical there, it should
be a virtual one. So in XEN 3.1 during the start of xen it will be created automatically like: 
veth1     Link encap:Ethernet  HWaddr 00:00:00:00:00:00  
          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
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
veth2     Link encap:Ethernet  HWaddr 00:00:00:00:00:00  
          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
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
but in the XEN 3.2 version, there is nothing like this. So as I know the developers have changed a lot.
Maybe this is one of the changes. But how can I add one of this interfaces again.
Hope my situation is now a little bit mor clear.
Thanks.
Cheers,
Maik