Re: Disabling ip4 and IPV6 on F20RC1

[Bjørn Mork <bjorn mork no>]

Pavel Simerda <psimerda redhat com> writes:

> > > 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.

This doesn't make any sense.  "manually configured" is not an address
type.  Both link local and global addresses can be manually configured
in the sense that the interface identifier can be manually configured.

> 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.

I don't know anything about OpenVZ, but ppp links do of course
distinguish between link-local and global addresses. The most important
difference is that a link-local address is required.  Please read RFC
5072.  The interface identifier is negotiated as part of IPV6CP and a
link local address is formed based on this.

The Linux kernel does of course also distinguish between link-local and
global addresses, regardless of interface type.  So also for ppp
interfaces.  For example (yes, this is a standard Debian stable kernel):

bjorn canardo:~$ ifconfig ppp0
ppp0      Link encap:Point-to-Point Protocol  
          inet6 addr: 2001:4620:9::1/128 Scope:Global
          inet6 addr: 2001:4600:10:101::c/64 Scope:Global
          inet6 addr: fe80::c/10 Scope:Link
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1452  Metric:1
          RX packets:10839512 errors:0 dropped:0 overruns:0 frame:0
          TX packets:13268759 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3 
          RX bytes:3067961018 (2.8 GiB)  TX bytes:1721577126 (1.6 GiB)


Link local and global addresses are not interchangable.  They have
different properties.  The difference is pretty obvious from the
names. You can easily see this on a host trying to ping either type of
local address, with and without an interface specifier.

> There's actually no reason you would need link-local addresses for
> static configuration.

I hear you say that.  You are wrong.



Bjørn