Subject: Re: illegal network routes and a ponderance
To: None <>
From: None <>
List: tech-net
Date: 02/18/2003 14:56:52
On Tuesday 18 February 2003 13:33, der Mouse wrote:
> >> What's going on here is that the network configuration is inherently
> >> illegal, because the "default gateway" you're being fed isn't on any
> >> network they've allocated you an address on.
> > Whether the network configuration is illegal or not, would it be
> > beneficial to allow this kind of routing?
> *What* kind of routing?
> What would it even _mean_ to have a route pointing to a gateway that's
> not on-net for any configured interface address?  Where would you
> expect such packets to be sent?  I can't see anything sensible to do
> with them.

The kind of routing where multiple default routes are possible; Where 
communicating with an ethernet-connected gateway that isn't in your specific 
netmask is simple; where outgoing traffic goes to the logical (as in 
sensible) interface it should; where ipfilter rules aren't needed to 
short-circuit the routing table.

Thor originally mentioned:

"There are a number of tricks you can use here; all are foul; some may
actually work." -- And then continued on to describe a way to use NAT along 
with an IP alias that *was not* allocated to one's own machine to work around 
the routing limitations.

By "foul" I suppose he could've just meant foul as in distasteful and 
hackish--smelly. But then, of course, that's what we all call Linux when it 
does something "incorrectly" or messily. I took "foul" to mean "wrong any way 
you look at it."

It's been mentioned that the only reason these kinds of routes exist are 
misconfigurations and ancient out-of-date equipment.

If we're discarding out-of-date equipment then why port to the older 

If we're inoperable in the face of misconfigurations, then we lose out because 
the philosophy appears to be--"Fix the configuration" when that's not always 
possible. Forcing purity on ourselves is fine, but all it does it piss 
everyone else off. Self-flagellation is (apparently) soul-purifying but when 
you turn the whip on people minding their own business, the results can be 

My original point was that in the interests of interoperability with networks 
where Linux chugs along just fine, perhaps this might be something to look at 
rather than forcing the whole network into "correctness" just to add NetBSD 
to the lot.

Current Telus ADSL gateways have multiple aliases and in some cases hand out 
the wrong gateway for the IP they just leased. I wouldn't say a suddenly 
disconnected machine is a big win here.

*Many* ethernet segments are shared by multiple networks. Regardless of how 
"correct" such a configuration is, the fact remains that in order to 
communicate with these foreign-local networks the NetBSD user must jump 
through some pretty crazy friggin' hoops.