Hi Michael!
Announcing 0.0.0.0/0 can really be a problem, but why
does BATMAN tunnel
the internet-traffic through gate0?
Because we want to have the means to select the gateway from the gateway
client, rather than ending up somewhere random with our outgoing Internet
traffic. With default route entries in every mesh node all a gateway client node
can determine is its next link-local hop on the path towards one of the
gateways. Hence every node on your path will make its own selection for the
default gateway, so it is not possible to select the gateway from the mesh
gateway client.
Cheers,
Elektra