Another IPv6 problem

[Michael H. Warfield]

Hey all,

	I've run into another problem with IPv6 and FC6.  This one is not a
"show stopper" (which it would be too late for, anyways) and more of an
extreme annoyance and install problem.

	I just went to install FC6 into one of my networks which uses static
IPv4 addresses and stateless autoconf for IPv6.  Guess what.  Can't do
it.  If you specify a static IPv4 address in the install, you also have
to specify a static IPv6 address if you have IPv6 enabled.  That sucks
out loud.  IPv6 and IPv4 configurations are independent.

	What's worse, I now realize, is that if you are using dhcp for IPv4,
it's also attempting to use dhcp6 for IPv6!  Gag!  That can result in
terrible slowdowns for network startup in IPv6 environments which are
only using stateless autoconf, whether you are using dhcp for IPv4 or
static IPv4 addresses.  If people are wondering why their FC6 installs
take forever to configure their network interfaces - surprise, you've
got IPv6 enabled and are using dhcp for IPv4 and don't have an IPv6
dhcp6 server.  Let the bitching begin.

	Bascally, someone was thinking in terms of IPv4 think when they
designed the installer and took no allowance for IPv6 autoconf (which
should be the most common method) and assumed that if you had IPv4 dhcp
you would have IPv6 dhcp, which is patently not a valid assumption at
all.  There are certainly reasons and advantages to having a dhcp6
server, but I'm just betting that very few installations are going to.

	The choices for IPv4 and IPv6 are orthogonal and different.

	IPv4:	dhcp  / static / disabled
	IPv6:	dhcp6 / static / autoconf

	If IPv6 is loaded, there appears to be no practical way to "disable"
IPv6 on an interface and the default is for "stateless autoconf" if IPv6
forwarding is disabled (/etc/sysctl.conf).

	Workaround is to disable IPv6 on that interface at install.  It really
doesn't disable IPv6 at all, it still configures and will then autoconf,
if you have IPv6 forwarding disabled).  So, "disabling" IPv6 has exactly
the opposite effect and results in it being enabled and autoconf'ed
properly.  Some of life's little ironies.

	Regards,
	Mike
-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
 PGP Key: 0xDF1DD471        | possible worlds.  A pessimist is sure of it!

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