Linux Ethernet Bridging - Apr 2007 - [Bridge] device eth0 is already a member of a bridge; can't enslave it to bridge Net6

Hello,
I am working on Network-Simulation (VNUML). Our simulator uses linux bridging to
connect the UMLs.
So there is one problem:
The example is the following: There are two hosts simulating one big net.
The two hosts have connection over the external nets Net3 and Net6 (see
http://www.uni-koblenz.de/~timbub/verteilteSim3.GIF), but in fact there is only
one physical connection between the host: connected through a switch an each
host has one interface card eth0. (so normaly you should bind the ip adresses
related Net3 and to Net6 to the eth0 and it already is part of the two nets -
even if there is one phsical connection)

So my virtual nets are implemented by linux bridges. But if I now connect the
physical interface eth0 to the bridge Net3 and then to Net6 the following error
occurs: "device eth0 is already a member of a bridge; can't enslave it
to bridge Net6"
Is this a bug or a feature? Why is it not allowed to bind an Interface to two
different bridges?
Is there a workaround for this issue?


Problem: 
UML1 ---- bridge1  \
                             eth0  
UML2 ---- bridge2  /


Workaround?:
UML1 ---- bridge1  \
                             bridge3 ---- eth0
UML2 ---- bridge2  /


UML1   \
             bridge1 ---- eth0
UML2   /



Thanks for your help
Tim Keupen
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Hello,
I am working on Network-Simulation (VNUML). Our simulator uses linux bridging to
connect the UMLs.
So there is one problem:
The example is the following: There are two hosts simulating one big net.
The two hosts have connection over the external nets Net3 and Net6 (see
http://www.uni-koblenz.de/~timbub/verteilteSim3.GIF), but in fact there is only
one physical connection between the host: connected through a switch an each
host has one interface card eth0. (so normaly you should bind the ip adresses
related Net3 and to Net6 to the eth0 and it already is part of the two nets -
even if there is one phsical connection)

So my virtual nets are implemented by linux bridges. But if I now connect the
physical interface eth0 to the bridge Net3 and then to Net6 the following error
occurs: "device eth0 is already a member of a bridge; can't enslave it
to bridge Net6"
Is this a bug or a feature? Why is it not allowed to bind an Interface to two
different bridges?
Is there a workaround for this issue?


Problem: 
UML1 ---- bridge1  \
                             eth0  
UML2 ---- bridge2  /


Workaround?:
UML1 ---- bridge1  \
                             bridge3 ---- eth0
UML2 ---- bridge2  /


UML1   \
             bridge1 ---- eth0
UML2   /



Thanks for your help
Tim Keupen
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