Re: Disabling ip4 and IPV6 on F20RC1

[Dan Williams <dcbw redhat com>]

On Sun, 2013-12-15 at 06:37 +0100, Robert M. Albrecht wrote:
> Hi,
>
> my system has a built in ethernet interface wich is working perfectly
> fine on IPV4 and IPV6.
>
> I added a second interface via usb for wiresharking some stuff (this way
> I don't get my own traffic in the packet dumps).
>
> I don't want or need an IP-stack on this second interface.
>
> In network manager there is on top of the IPV4 and IPV6 config pages an
> on/off button.

When you say "in network manager", do you mean the GNOME system settings
application, in the network panel?  There are on/off slider switches
there for both IPv4 and IPv6, and if they value does not stick, then
that is a bug in the GNOME control center.

> For IPV4 this buttons seems to have no effect at all. It's off-position
> is not even saved when applying or closing the dialog.
>
> For IPV6 something happens. All addresses except local link are deleted,
> no DNS and routing.

NetworkManager 0.9.8 and lower implement an "IPv6 ignored" option to
remain compatible with the long time ago when NetworkManager did not
support IPv6 at all.  This is likely what the "off" button is doing in
the GUI you are using.  It doesn't actually mean IPv6 is disabled for
the interface, it simply means that NetworkManager will not perform any
IPv6 addressing itself.

However, the *kernel* does do IPv6 link-local addressing, and will also
do IPv6 SLAAC if you've let it.  So just because NetworkManager isn't
doing any IPv6 configuration, that doesn't mean something else isn't.

NetworkManager 0.9.9+ may implement actual IPv6 disabling, but we
haven't heard of a great use-case for it, since having an IPv6
Link-Local address on the interface (which the kernel will always
provide) is almost never a problem, even with FCoE.

> But if link local still remains where is the difference between
> disabling IPV6 or enabling and choosing link local configuration only ?

If IPv6 is "ignored" (ie, the "off" button), NetworkManager will not
process any IPv6 Router Advertisements and will not set up a global IPv6
address on your interface, and will not process any DNS servers or
search domains from the Router Advertisement either.  It will also not
perform DHCPv6 addressing, either alone or as requested by the IPv6
router.

Dan

> Did I missunderstand the gui and the on/off buttons have some other
> effect ? Or is it simply broken ?
>
> cu romal
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