Re: Disabling ip4 and IPV6 on F20RC1

----- Original Message -----
From: "Tore Anderson" <tore fud no>
To: "Pavel Simerda" <psimerda redhat com>
Cc: networkmanager-list gnome org
Sent: Tuesday, December 17, 2013 12:19:44 PM
Subject: Re: Disabling ip4 and IPV6 on F20RC1

* Pavel Simerda

1) First of all it doesn't *specifically* disable kenrel link-local
addresses allocation but performs some magic to disable a couple of
IPv6 features at once. This wouldn't be a problem in the original
poster's case as he wants to disable IPv6 anyway.

As I understand it, link-local addressing is necessary for IPv6 to
function at all.

Nope. IPv6 can work just as well as IPv4 with manually configured addresses. It's described in the resource I 
linked to. For example OpenVZ (must be used with a patched kernel) does that for its venet virtual networking 
infrastructure. Another example is a ppp links (with normal kernels) don't even distinguish the link-local 
and global addresses. There's actually no reason you would need link-local addresses for static configuration.

So disabling link-local addressing is analogous to disabling IPv6.

I understand the source of this idea but I believe it is a mistake and source of problems.

It would be
like removing the lowest floor of a building and expecting the remainder
to *not* come crashing down... :-)

The problem with analogies is that they usually don't work as well as pure technical reasoning. Communication 
between two global IPv6 addresses doesn't rely on link-local addresses at all (neighbor solicitations and 
advertisements use the global addresses in that case). Anyone who says something different should back up his 
claim on technical basis.

2) But setting disable_ipv6 doesn't really work as expected. See [1]
and especially the note about disable_ipv6 below the table. The truth
is that this also wouldn't affect the original poster's use case
where the specific interface is (hopefully) expected to be always
without IP addresses.

Okay. I'm not sure I've understood what the bug in question is and how
to tickle it, though.

I think it's described in one of the upstream bug reports but I can't find it right now. The only thing you 
can do if we don't find a description is to try it yourself.



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