Subject: RE: ... Allow router to be 0.0.0.0?

From: Bernie Volz <[email-masked]>
Date: Thu, 22 Jun 2000 21:39:36 -0400

John:

The 0.0.0.0 as the default route convention is for the DESTINATION, not the
ROUTER. We're talking about specifying the ROUTER'S IP ADDRESS as 0.0.0.0.
That is, obviously, not a legal address for a router. Thus, there is no
other use of that address.

A default route, if allowed in CSR (as it is currently), is specified as a 0
subnet mask length.

Thus, if you wanted to specify that all addresses should be ARPed for, you
might send a CSR option with data as: 00:00:00:00:00. The means 0 subnet
bits (hence no subnet number) followed by the 0.0.0.0 router IP address.

If you wanted to install a route that say the 10 network is local, you'd use
08:0a:00:00:00:00. 08 for the subnet bits, 0a for the subnet number (10),
and 0.0.0.0 for the router.

If you wanted to install a routes that say the 10 network is local and for
the 11 network use the router at 10.0.0.1, you'd specify:
08:0a:00:00:00:00:08:0b:0a:00:00:01.

See the CSR document for encoding information.

Hope that helps.

- Bernie Volz
  IPWorks, Inc.

-----Original Message-----
From: John Schnizlein [mailto:[email-masked]]
Sent: Thursday, June 22, 2000 8:43 PM
To: [email-masked]; DHCPv4 discussion list
Subject: RE:... Allow router to be 0.0.0.0?

Please persuade me that this will not cause any confusion 
with the common use of 0.0.0.0 as a default route.
It should not imply that the host infer proxy arp for all
addresses, following Ted's explanation below.
It should permit installing preferred routes through 
different routers on the directly-attached subnet.
John

At 06:10 PM 06/22/2000 -0400, Bernie Volz wrote:
>...
>By specifying 0.0.0.0, you set up a standard convention that 
>prevents the need for the server to change the option data and 
>makes it easy for clients to take whatever special action is 
>needed for them to install these routes.
>
>From: Ted Lemon [mailto:[email-masked]]
>...
>What this is is a limited form of the proxy arp feature in Windows,
>where if you give a windows machine its own IP address as a default
>route, it ARPs for every IP address it tries to contact, whether or
>not that IP address is on its local subnet.

---

From: Eric Michelsen <[email-masked]>
Date: Sun, 25 Jun 2000 23:58:08 -0700

I believe Windows allows the same "convention" that Linux does: if you
specify your own IP address as the *next-hop* for *any* route, then the
machine ARPs directly for that address, regardless of its subnet.  This has
nothing to do with the destination value or mask.    You never use a value
of zero for the next-hop.

For example, if my IP address is 192.168.1.2/24, then a route of

dest=172.16.0.0/16 next-hop=192.168.1.2

causes me to ARP directly for anything on 172.16.0.0, even though it's not
on my subnet.

If it happens that I use my own IP address as the next-hop for the default
route, then so be it.  All destinations not covered by more specific routes
get the "local ARP convention:"

dest=0.0.0.0/0 next-hop=192.168.1.2.
-------------------------------------------
Eric L. Michelsen, Copper Mountain Networks 

> From: Bernie Volz [mailto:[email-masked]]
> Sent: Thursday, June 22, 2000 18:40
> To: DHCPv4 discussion list
> Subject: RE: ... Allow router to be 0.0.0.0?
> 
> 
> John:
>

---

From: Bernie Volz <[email-masked]>
Date: Mon, 26 Jun 2000 20:59:31 -0400

Eric:

I don't understand your comment.

I'm saying that for a local route, we want to specify 0.0.0.0 as the router
in the CSR option. The client would substitute ITS LOCAL IP ADDRESS to
install that route, for the router, on Windows and Linux. For other
platforms, it does whatever it needs to do.

If we made the CSR option specify the host's IP Address, then the DHCP
Server would have to construct a unique CSR option for each host. Not a nice
thing, IMHO, since the server would (a) have to treat this option as special
and (b) have some mechanism for the user to request the behavoir on a
specific route.

By using the 0.0.0.0 convention, you solve both these problems. Of course
the host can't use 0.0.0.0 as the router and must do whatever is necessary
for the destination to be local, if that is something it can support.

- Bernie Volz

---

From: Eric Michelsen <[email-masked]>
Date: Mon, 26 Jun 2000 20:39:02 -0700

Sorry, I think I misunderstood the question.  Yes, I agree with Bernie,
below.
-------------------------------------------
Eric L. Michelsen, Copper Mountain Networks 

> Sent: Monday, June 26, 2000 18:00
> Cc: [email-masked]'