Hi. /31 on ethernet links

Sebastian Hyrwall sh at keff.org
Fri Oct 30 23:19:47 UTC 2009

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 inet
> ...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 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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