Re: route command cannot set up route through point-to-point interface

[der Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> What is necessary is is that each node have one (or more) IP
> addresses,

Even this much isn't really true, if (a) the node in question never
needs to be addressed directly (ie, it's just routing packets, not
being an endpoint), (b) you don't mind losing things like ICMPs that
might otherwise be emitted by it, and (c) all of its peers are content
without its having an address on the relevant interfaces.

> Way back when, [...].  Given that, it was natural to require two
> addresses when ifconfiging, but as you say, in principle it's not
> necessary.

Even systems that do demand that .2. links have addresses don't always
demand that they have distinct addresses.  I've got some systems on
which a single address is shared by multiple .2. endpoints.  For
example, excerpted from "ifconfig -au" on one of my live systems just
now:

tun1: flags=8011<UP,POINTOPOINT,MULTICAST> mtu 1500
        inet 10.0.5.1 --> 10.0.5.2 netmask 0xffffffff 
tun2: flags=8011<UP,POINTOPOINT,MULTICAST> mtu 1500
        inet 10.0.5.1 --> 10.0.5.3 netmask 0xffffffff 
tun3: flags=8011<UP,POINTOPOINT,MULTICAST> mtu 1280
        inet 10.0.5.1 --> 10.0.5.5 netmask 0xffffffff 
tun4: flags=8011<UP,POINTOPOINT,MULTICAST> mtu 1500
        inet 10.0.5.1 --> 10.0.5.6 netmask 0xffffffff 
tun5: flags=8011<UP,POINTOPOINT,MULTICAST> mtu 1500
        inet 10.0.5.1 --> 10.0.5.7 netmask 0xffffffff 

I've also done something similar where the shared address also belongs
to a broadcast interface on the host, as in

le0: 10.0.1.1/24
tun0: 10.0.1.1 --> 10.0.2.1
tun1: 10.0.1.1 --> 10.0.3.1

For some purposes - eg, administrative purposes under some address
assignment schemes - a nondistinct address like this is as good as no
address.

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