Xen users - Nov 2012 - External Network dhcp problems

Hello,

I have set up an external network on my dom0 xcp server and use an external dhcp
server/ internet gateway. Creating a PV ubuntu 12.04 VM using the automatically
created Networkbridges "Network X" works without a problem, as the VM
is able to retrieve an IP address. When I connect the VM to the external network
created via Xencenter, it is not able to get an IP address. What am I doing
wrong?

Here are further informations

XCP version 1.6.07
XCP build number 61365c (the problem occurred with the previous version too)
External Network name: Harlan - Harmony - Netzwerk
XCP dom0 server name: flicka
Xencenter version: 6.1
The external network has the VLAN Tag 1
following: xe pif-list, xe network-list, xe vif-list, xe vm-vif-list, xe vm-list


[root@flicka ~]# xe pif-list
uuid ( RO)                  : 50e0e678-e798-79f0-a4c4-e9dc4ae42ec6
                device ( RO): eth1
    currently-attached ( RO): true
                  VLAN ( RO): -1
          network-uuid ( RO): 64bc3ee4-3ebe-b2a7-a327-30537277f845


uuid ( RO)                  : 02336de2-39cb-3958-46ec-1ac8822dad8d
                device ( RO): eth4
    currently-attached ( RO): true
                  VLAN ( RO): -1
          network-uuid ( RO): a724a580-355a-a440-de45-5c1653087413


uuid ( RO)                  : 003e5dee-a64f-91ae-d0e3-43f717e88bf9
                device ( RO): eth3
    currently-attached ( RO): true
                  VLAN ( RO): -1
          network-uuid ( RO): be0dd0a8-9386-9b00-16f0-064ec762f56e


uuid ( RO)                  : 65601b85-90d8-34e2-3950-3fe39122f1e8
                device ( RO): eth5
    currently-attached ( RO): true
                  VLAN ( RO): -1
          network-uuid ( RO): e6d780d8-6aef-6d8f-6348-43011ef1dbad


uuid ( RO)                  : 47cb3080-54e4-3e17-70fd-14c059ac2437
                device ( RO): eth4
    currently-attached ( RO): false
                  VLAN ( RO): 1
          network-uuid ( RO): f9732d94-bf77-6738-31b5-ec11b4d77760


uuid ( RO)                  : 389df5de-a8d2-d8ad-6386-ea68b7dbfe45
                device ( RO): eth0
    currently-attached ( RO): true
                  VLAN ( RO): -1
          network-uuid ( RO): c92cf8c5-3eb8-5f61-cf5e-fa92fa511049


uuid ( RO)                  : c772ca35-07ae-2a59-e2a5-fe612b0353cd
                device ( RO): eth2
    currently-attached ( RO): true
                  VLAN ( RO): -1
          network-uuid ( RO): f8db3853-afec-efec-74fb-7f0b634b6e1e








[root@flicka ~]# xe network-list
uuid ( RO)                : 0f415cd6-a248-a23d-c15f-24ec43ec9a34
          name-label ( RW): Host internal management network
    name-description ( RW): Network on which guests will be assigned a private
link-local IP address which can be used to talk XenAPI
              bridge ( RO): xenapi


uuid ( RO)                : a724a580-355a-a440-de45-5c1653087413
          name-label ( RW): Pool-wide network associated with eth4
    name-description ( RW):
              bridge ( RO): xenbr4


uuid ( RO)                : e6d780d8-6aef-6d8f-6348-43011ef1dbad
          name-label ( RW): Pool-wide network associated with eth5
    name-description ( RW):
              bridge ( RO): xenbr5


uuid ( RO)                : be0dd0a8-9386-9b00-16f0-064ec762f56e
          name-label ( RW): Pool-wide network associated with eth3
    name-description ( RW):
              bridge ( RO): xenbr3


uuid ( RO)                : c92cf8c5-3eb8-5f61-cf5e-fa92fa511049
          name-label ( RW): Pool-wide network associated with eth0
    name-description ( RW):
              bridge ( RO): xenbr0


uuid ( RO)                : 64bc3ee4-3ebe-b2a7-a327-30537277f845
          name-label ( RW): Pool-wide network associated with eth1
    name-description ( RW):
              bridge ( RO): xenbr1


uuid ( RO)                : f8db3853-afec-efec-74fb-7f0b634b6e1e
          name-label ( RW): Pool-wide network associated with eth2
    name-description ( RW):
              bridge ( RO): xenbr2


uuid ( RO)                : f9732d94-bf77-6738-31b5-ec11b4d77760
          name-label ( RW): Harlan - Harmony - Netzwerk
    name-description ( RW): TV - Server Harmony und owncloud - Server Harlan auf
:D8
              bridge ( RO): xapi0






[root@flicka ~]# xe vif-list
uuid ( RO)            : 3aa9a6e6-a430-6588-9f8e-b7e37e6990c9
         vm-uuid ( RO): 064be010-2877-aaf2-6a1c-24e3d4dd8e98
          device ( RO): 1
    network-uuid ( RO): f9732d94-bf77-6738-31b5-ec11b4d77760




[root@flicka ~]# xe vm-vif-list
uuid ( RO)                  : 3aa9a6e6-a430-6588-9f8e-b7e37e6990c9
         vm-name-label ( RO): Harlan
                device ( RO): 1
                   MAC ( RO): b2:ef:51:61:de:4e
          network-uuid ( RO): f9732d94-bf77-6738-31b5-ec11b4d77760
    network-name-label ( RO): Harlan - Harmony - Netzwerk





[root@flicka ~]# xe vm-list
uuid ( RO)           : 064be010-2877-aaf2-6a1c-24e3d4dd8e98
     name-label ( RW): Harlan
    power-state ( RO): running


uuid ( RO)           : f37e707a-04ac-48ad-b693-0d017aaf6cdd
     name-label ( RW): Control domain on host: flicka
    power-state ( RO): running

I would appreciate any help regarding this issue

kind regards,
Markus