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From: Julian Elischer <julian@ref.tfs.com>
Message-Id: <199510302322.PAA13352@ref.tfs.com>
Subject: Re: Unnumbered Interfaces
To: dennis@etinc.com (dennis)
Date: Mon, 30 Oct 1995 15:22:09 -0800 (PST)
Cc: hackers@freebsd.org
In-Reply-To: <199510302311.SAA18575@etinc.com> from "dennis" at Oct 30, 95 06:11:48 pm
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> 
> >define un-numbered interfaces..
> 
> This seems to be the standard reply here...so here goes...
> 
> Most routers have an option (which everyone seems to like) that
> allows a serial interface to be defined without a local address.
> This allows all interfaces on the machine to have the same address,
> almost always the primary ethernet address.  For Example...
> 
> ed0     Address: 192.1.1.1
> ser0   PTP Address 211.14.17.1
> ser1   PTP Address:215.27.1.1
> 
> When using unnumbered interfaces, all of the interfaces have a "local" address
> of 192.1.1.1. This is nice because all transactions from the host have the same
> source address, and you also save addresses by not having to use one for each

As far as I know this has always worked under BSD since 4.2

> logical or physical connection. Another and perhaps better  method would be to 
> have a host address for the machine, which would be applied as the source
> address
> for all unnumbered interfaces. It allows for the appearence of a single IP
> entity to
> the outside world, which of course is what a single host really is.
> 
> Given that unix really resolves to a pointer (internally) and the local
> address is
> only used for reference....I would think that it can be done. You'd have to
> be able to 
> configure a PTP interface without a local address...
> 
> 
you use ifconfig with the same address as the primary enet,  but
give it a PTP address as well,
the routing code only looks at the REMOTE address to make decisions on
PTP links