Subject: Re: HEADS UP! Default value of ip6_v6only changed
To: NetBSD OS PMC <>
From: William Allen Simpson <>
List: tech-net
Date: 10/28/2003 04:54:30
NetBSD OS PMC wrote:
> The default value of ip6_v6only (sysctl net.inet6.ip6.v6only) has
> been changed.  The new value brings us closer in line with current
> RFC-defined behavior and practices.
> Itojun still has significant concerns about the new default behavior.
> His concerns have been well-documented in
> Best Regards,
> NetBSD OS PMC (core)

The draft is well founded.  I strongly opposed the translation/mapping 
of IPv4 into IPv6 a decade ago.  There was a whole working group 
devoted to the project, and AFAIK, the WG failed interoperability and 
was disbanded. 

The stack should use IPv4 or IPv6 on a per host basis, as indicated by 
its DNS *and* the availability of IPv6 infrastructure, but not both 
concurrently (for a host).  Of course, there could be IPv4 and IPv6 
concurrently (dual stack approach).

Craig Metz is a sharp fellow, and has been working on IPv6 
implementation since the beginning.  We all respect itojun (of course). 

RFCs are not gospel.  RFC-2133/2553/3493 has evolved over time, and is 
"Informational".  The new IPV6_V6ONLY is only in the most recent 
version, and the default value of "off" is manifestly wrong.  

Please leave the default value as "on", as recommended by 
William Allen Simpson
    Key fingerprint =  17 40 5E 67 15 6F 31 26  DD 0D B9 9B 6A 15 2C 32