[Babel-users] Multiple internet gateways in the mesh

[Juliusz Chroboczek]

> Do I want to install TWO default routes with my script, one to be used and
> one to be propagated?

Yes, I think you need to do that.  A route in Babel is either
redistributed (in which case it triggers duplicate suppression) or ignored
(in which case it's not redistributed).  If you need one route that
doesn't trigger duplicate detection, and one that does, then you need two
routes.

Note that the route being redistributed can have an arbitrarily high
kernel metric, and it can even be an unreachable route, so it doesn't
interfere with kernel routing.

> What I would like for most sites is that the daemon-installed route has
> a high metric, and the Babel-installed route has a low metric, so that
> traffic flows away from that site in the mesh, and out through the
> preferred link.

In that case, you need a dedicated router to handle the uplink.  In the
following, "border router" is the router that handles the uplink, and
"access router" are the other routers at the local site.

On the border router, say

  out ip 0.0.0.0/0 le 0 metric 16384

The border router will still use the local uplink, but it will announce
a route with a very high metric to its neighbours, which will cause the
access routers to prefer a different route if one is available.

I don't see a good way to achieve that if the border router is also the
access router.  Let me know if that's one of your requirements, and I'll
see if I can work out a solution.

-- Juliusz