Re: host route out of subnet

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

On Fri, Feb 27, 2015 at 10:21:27AM -0500, Mouse wrote:
> > We have a wiki on it here:
> > http://www.netbsd.org/docs/network/#nonsubnetgateway
> 
> ..."the gateway you need to route through may not be on the same subnet
> as the address assigned to your network interface".
> 
> That's an utterly bizarre way to set up a network and I'm not a bit
> surprised it's not well supported; indeed, I'm slightly surprised it's
> even possible to kludge it as you outline.  (I'm not surprised it
> happens, mind you.  Lots of brokenness happens.)

Strato has such a setup for all the root servers they rent out. I guess
they implement it by a strict Layer 2 filter policy in the switches in
combination with ARP filtering.

> If I were faced by such a thing, I'd either (a) add an address to my
> interface that's on-subnet for the gateway, or (b) do that once and ARP
> to get the MAC, then hardwire an ARP entry for a fictitions address
> that _is_ on my subnet and configure that as my gateway.  I even recall
> doing (b) once, though I don't recall details.

You have no subnet @Strato. You have a single /32 and a single IP that
is willing to route your traffic. What the interface route is giving you
is effectively point-to-point over Ethernet.

Joerg