Subject: Re: Routed, anyone?
To: None <current-users@NetBSD.ORG>
From: Greg Earle <earle@isolar.Tujunga.CA.US>
List: current-users
Date: 03/07/1996 14:44:13
>> Why are you using anything but static routes?
> Probably to advertise the local net to the ISP, so it knows how to
> route to it.

I believe the original poster only mentioned having a NetBSD box and a Mac.
No real need to advertise a whole "local net" in this case.

>> There is no need here to use the routed.  Unless your advertising
>> like 40 different routes.  Just put the routes in and leave them.
> How?  The ISP's gateway box is one place you'd need to add static
> routes to obey your advice.


> Mind you, having it listen to routing info is dubious in any case; the
> next dialup user could also start advertising routes to your machines,
> and the router won't know which to believe.

Precisely.  Any ISP that would listen to RIP on their incoming PPP links is
an idiot.

>>> Anyone know how to tell routed not to delete a particular route,
>>> every time?
>> Yes, don't run it use static routes.
> If you think it can be done with static routes, please explain how.
> Don't forget to explain how the ISP's router box discovers where to
> send packets for boxes behind the dialup machine.

Well, as Ken Horenstein just alluded to, a real easy way is to use a 2-bit
subnet on the home machine.  That means the ISP end merely has to Proxy ARP
for your two hosts at home, and add one little static route to your other
(non-PPP endpoint) host.

When I set up my PPP link at home, this is precisely what I did.  I chose
.254 for my home machine address (a SPARCstation 1 clone box) and chose .253
for our Mac Duo 230.  The SPARC box uses a netmask, whereas
the machines at work (other end of the PPP link) use a standard

The only downside of this is that it makes x.y.z.252 a net address by default,
and that's the address of my NetBSD box at work  :-)  I could move my NetBSD
system at work to another address and resolve the problem that way; as is, I
can work around it by deleting the net route on the SPARC machine at home
(which gets created automatically from having the netmask)
and the default picks it up.  I also add a host route to the Mac on the SPARC
box side so it doesn't try to go the wrong way.  The only problem with this
workaround is that the Mac doesn't know how to delete net routes (even
Open Transport can't), so my Mac can't directly connect to the NetBSD box at
work.  This has not proven to be a major problem in practice, however.

This approach only requires adding 3 lines to /etc/rc.local on the remote end.
On the local end I use 1 route add default, 2 route delete nets and 2 route
add host commands to work around the above circumstances.  Works great for me.

	- Greg