Bridge with 1x eth and 2x tun, adding 2nd eth, hosts become unavailable

["Marc Roos" <M.Roos@xxxxxxxxxxxxxxxxx>]

In this situation I can ping a vm from br0 connected to 172.16.1.y



               +-----------+           
               |    BR0    |           
   172.16.1.y  |           |      172.16.1.x
       --------|ETH2   TUN1|-------           
               |           |           
               |           |      172.16.1.x
               |       TUN2|-------           
               |           |
               +-----------+ 

When only adding a 2nd eth adapter with 'brctl addif br0 eth1' connected 
to 10.11.12.y. The same ping is not working anymore.


               +-----------+           
               |    BR0    |           
   172.16.1.y  |           |      172.16.1.x
       --------|ETH2   TUN1|-------           
               |           |           
               |           |      172.16.1.x
    10.11.12.y |       TUN2|-------           
       --------|ETH1       |
               +-----------+           
			             
When I remove the eth1 again, the ping starts working again.

Can someone explain me why the bridge is behaving like this? And how 
this can be fixed?