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Re: prefixlen of IPv6 over PPP

On Nov 6, 2009, at 12:46 PM, Nagae Hidetake wrote:

From: "Brian A. Seklecki" <>
Subject: Re: prefixlen of IPv6 over PPP
Date: Fri, 06 Nov 2009 11:43:41 -0500

Very curious.  check some RFCs, or check an XP box.  What is RTADV
giving them and what are they accepting?

Assigning a /128 to an v6 PPP interface is like assiging a /32 to an
IPv4 (/31 is...maybe known to work in some exotic platforms, but..)

In Section 4.1 (Interface Identifier) of RFC 5072 (IP Version 6 over PPP):

 This Configuration Option provides a way to negotiate a unique, 64-
 bit interface identifier to be used for the address autoconfiguration
 [3] at the local end of the link (see Section 5).

In Section 5.3 (Creation of Link-Local Addresses) of RFC 4862 (IPv6
Stateless Address Autoconfiguration):

 If the sum of the link-local prefix length and N is larger than 128,
 autoconfiguration fails and manual configuration is required.

So I think prefixlen should be 64, but I'm not sure...

I wonder if the problem is that it's a ppp interface. Stateless autoconfig is defined for Ethernet-like devices with 6-byte MAC addresses that are expanded to 8 bytes per an algorithm. Maybe the NetBSD code doesn't handle the ppp interface type properly with a 64- bit prefix.

                --Steve Bellovin,

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