[atlas] Probe on a /31 or /32 IPv4 network

On Fri, Aug 15, 2014 at 06:23:09AM +0200, Mikael Abrahamsson wrote:
> On Thu, 14 Aug 2014, Baptiste Jonglez wrote:
> 
> >Using a gateway that is not on the same subnet doesn't sound very nice,
> >but again, the goal is to avoid wasting precious IPv4 space.
> 
> What router platform are you using upstream from the probe? Doing a /32 per
> vlan(ie sharing a larger subnet between different vlans) is perfectly
> possible on several routing platforms.

We're using Linux.  Actually, we are already routing a /32 per VLAN on the
router, but up to now, we were also setting up /32 "subnets" on the
downstream routers or hosts.

> http://tools.ietf.org/html/rfc3069.html

Interesting read.  It basically amounts to use /32 routes on the router,
and a larger subnet (e.g. /24) on hosts, as Philip suggests.

This is a bit of a hack when hosts want to talk to each other, but this is
mostly ok for the probe (or we can use proxy ARP on the router if it
becomes a problem).

Thanks for the help,
Baptiste
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