This behavior is hardly shameful; it's just old. It was entirely
appropriate for a router in the original view of what a router was.
Over the years that view has evolved. It's typical of such evolutions
that distinctions get blurred and people forget history, and that is
what has happened here.
Originally, a router was viewed as a device that linked networks:
hence the things it connected to were presumed to be networks, and
that presumption was built into their code. When routers were linked
with serial lines, those lines had to look like networks. "Network"
evolved pretty quickly into "subnet", and serial lines were run as
subnets with /30 masks - 4 addresses: network number, IP for each end,
and broadcast address.
A router links networks and has an IP in each one. Call this
perspective the traditional big network router perspective.
A host originally was a box on a network. It had an IP address - one
IP address. When people started using SLIP and PPP to link hosts
together, most of them thought in terms of single-IP boxes. As they
began to use their hosts for routing, their perspective was one of
point to point links linking routers, not routers linking networks.
A router has one IP and is linked to other routers by PTP links and
networks. Call this the perspective of small-network origin.
Neither perspective is "right" or "wrong", but they do affect how
people look at the world. Since routing is based on networks, the
perspective that routers connect networks is arguably more natural,
although probably most people on this list would see it the other way
around.
I came out of the router heritage, and for me the notion that a router
could have the same IP address on more than one interface took some
getting used to.
-- Dick St.Peters, stpeters@NetHeaven.com Gatekeeper, NetHeaven, Ballston Spa, NY, 1-800-910-6671 (voice) Albany/Saratoga/Glens Falls/North Creek/Lake Placid/Blue Mountain Lake First Internet service based in the 518 area code