Linux bridging UMTS <-> eth0

Hi

I am setting up a bridg for use wit a UMTS USB modem (ubuntu 9.04)

I want the following solution:
roaming gprs modem | <=USB0=> | ppp0 ubuntu server br0 | eth0

I have testet with this solution (/etc/network/interfaces) without any luck.

auto lo
iface lo inet loopback

# Configure br0 using ifupdown with dhcp and add eth0 to the bridge
auto br0
iface br0 inet dhcp
      bridge_ports eth0

# udev calls ifupdown for usb0 when it is created and destroyed.  See /etc/udev/rules.d/85-ifupdown.rules
# Tell ifupdown not to assign an IP address and add it to the bridge.
auto usb0
iface usb0 inet manual
      up ifconfig $IFACE 0.0.0.0 up
      post-up brctl addif br0 usb0

> brctl show shows ony the one endpoint (eth0)

Have anyone a pointer or a solution to this?

RGDS
N2WehaAsked:
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OliverRahnerCommented:
Try the following, for diagnosis:

- bring up your UMTS-connection
- note the IP address of usb0
- enter the following commands:
  ifconfig br0 #.#.#.# #.#.#.# (ip adress and subnet mask of usb0)
  ifconfig usb0 0.0.0.0
- add usb0 manually to the bridge
  brctl addif br0 usb0
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N2WehaAuthor Commented:
Sorry about this very late answer. Summer holidays.

The solution using  USB0 is not viable since USB0 is on a PPP connection.

I found a solution using a firewall and DHCP.

Best regards
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