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Date:      Sat, 31 Oct 2009 02:21:34 +0100
From:      Sebastian Hyrwall <sh@keff.org>
To:        Chuck Swiger <cswiger@mac.com>
Cc:        freebsd-net@freebsd.org
Subject:   Re: Hi. /31 on ethernet links
Message-ID:  <4AEB911E.1070104@keff.org>
In-Reply-To: <BCE5F8B9-D52A-4F58-A5B9-DDDCF78B7D1B@mac.com>
References:  <4AEB7AE8.5090101@keff.org> <18C758A7-1908-4D1A-BDCA-80FF7FD8BC22@mac.com> <4AEB834D.1050907@keff.org> <BCE5F8B9-D52A-4F58-A5B9-DDDCF78B7D1B@mac.com>

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Chuck Swiger skrev:
> On Oct 30, 2009, at 5:22 PM, Sebastian Hyrwall wrote:
>>> A /31 subnet is only defined for point-to-point network links, per:
>>>
>>>  http://www.rfc-editor.org/rfc/rfc3021.txt
>>>
>>> Ordinary ethernet links have BROADCAST flag set instead of POINTOPOINT.
>>>
>>
>> Well how do I set the POINTOPOINT flag and remove the BROADCAST-flag 
>> on ethernet links? Or are you implying that it does not belong on 
>> ethernet links :)  Cause Cisco and Linux support /31 (ptp's) on 
>> ordinary ethernet links.
>
> Ethernet point-to-point links are normally handled by ppp / pppd in 
> PPPoE mode, but possibly something like:
>
>   ifconfig en0 inet 192.1.1.10 inet 192.1.1.2
>
> ...would give you a POINTOPOINT link instead.  If not, you can 
> probably fake things out by either using a /30 and wrapping the /31 
> inside, or using  a /32 and an explicit default route via your 
> ethernet interface.
>
Unfortunetly that doesn't work. It just sets 192.1.1.2 as broadcast.

Well wrapping a /31 inside of a /30 kinda defeats the purpose :)


If Cisco,Linux and NetBSD support it so should FreeBSD imho.

> Regards,




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