Subject: RE: Help! Static route option

From: Bernie Volz <[email-masked]>
Date: Wed, 19 Jan 2000 09:45:18 -0400

Since this option goes back to the days of classful networking, it
would be assumed that the mask associated with the destination is
based on the class of the destination.

I could see TWO interpretations of the destination's host part not
being zero (based on the class mask):

1. Assume it is a HOST route. In this case, the mask would be
255.255.255.255.

2. Assume it is a NETWORK route. In this case, clear the host part.

I believe (1) is the behavoir you are seeing and is probably the
better behavoir since it allows both HOST and (classful) NETWORK
routes to be communicated.

- Bernie Volz
  Process Software

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Mail sent to [email-masked] by [email-masked]:

A quick question.

For the old DHCP Static Route Option (33) that has no mask, what is the
effective mask supposed to be?

Mac OS Open Transport currently uses a mask of all-ones, apparently in
the assumption that a route without a mask must necessarily be a host
route.

I'm wondering if maybe the intention of the Static Route Option was that
the mask should be derived programmatically from the class of the
destination address, in the old sense of Class A, Class B, Class C. In
other words, a route to destination 36.0.0.0 is assumed to have a /8 mask
because it is a Class A address. However, what would you do if the
destination were 36.17.23.194? That's a Class A address, but it has ones
in the host part, so it can't possibly be a route to net 36/8.

RFC 2132 doesn't provide any clarification on this.

(I know Static Route Pption is due to be replaced by "Static routes with
subnet masks option", but we'd still like to handle the old option in a
sane way too.)

Stuart Cheshire <[email-masked]>
   * <A HREF="http://ResComp.Stanford.EDU/~cheshire/">Web Page</A>
   * Wizard Without Portfolio, Apple Computer

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From: Ted Lemon <[email-masked]>
Date: Wed, 19 Jan 2000 18:12:50 -0500

I think it would be a mistake to even implement the static route
option at this point.   I still owe the WG a classless static route
option, which is what I would suggest you implement.   *blush*

			       _MelloN_

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From: Ralph Droms <[email-masked]>
Date: Thu, 20 Jan 2000 07:53:32 -0500

Interesting - I had always assumed 2 was right.  But the text in
RFC2132 doesn't give any hint, and both interpretations of RFC2132
are reasonable.

Although this option is to be superceded by an option with explicit
masks, we should come to consensus about an interpretation and
modify the text in the next rev of RFC2132.

- Ralph

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At 09:45 AM 1/19/00 -0400, Bernie Volz wrote:
>I believe (1) is the behavior you are seeing and is probably the
>better behavior since it allows both HOST and (classful) NETWORK

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From: Ted Lemon <[email-masked]>
Date: Thu, 20 Jan 2000 12:32:28 -0500

> modify the text in the next rev of RFC2132.

Is there any reason not to just say it's deprecated?   Whichever of
the two choices is correct, the option is really not useful - at this
juncture, it is sheer coincidence if the "class" subnet mask and the
classless subnet mask are the same, and sheer coincidence is a lousy
basis for network protocols.   :')

			       _MelloN_