Question about babel over bird

[Oriol Rico]

Hello:
    We have a series of wireless antennas deployed in mesh with the babel
protocol using bird.
   Two of those antennas advertise the route 10.0.0.0/8.
   The rest of the antennas choose one of the two outputs depending on the
babel protocol.
   How can I force it to go out through one or the other exit?

Thanks

Oriol