[CentOS] Two small issues after upgrade to 4.2 -- [OT] IPv4 LINKLOCAL

[Bryan J. Smith]

"Scot L. Harris" <webid at cfl.rr.com> wrote:
> zeroconf is what puts the 169.254.0.0 route in your routing
> table.  Look at netstat -rn to see it.
> Suppose to allow you to turn on a system without setting up
> any networking and the system is suppose to find other
> systems and self configure themselves into a network.  You
> can disable zeroconf by modifying /etc/sysconfig/network by
> setting the following:
>   nozeroconf = yes
> (again that may be in all caps, check the file)
> Have never seen this used for anything.  And don't expect
> to see it used any time soon.

Actually, the 169.254./16 network is IPv4 LINKLOCAL.
It is the IPv4 equivalent to FE80::/10, IPv6 LINKLOCAL.

I haven't kept up with various standardizations, it's not
only perfect normal to have both a 169.254./16 and another
IPv4 address on an interface, but it is encouraged for some
scenarios.  In other words, do not be bothered by the
existance of a 169.254./16 address on a IPv4 dynamically
assigned interface.

This will be such the case with IPv6.  All IPv6 nodes have a
LINKLOCAL address of FE80::/10, as well as another.  The
initial IPv6 design was to allow up to 3 -- LINKLOCAL
(FE80::/10), SITELOCAL (FEC0::/10) and then a public, but
SITELOCAL has been recently deprecated (even if not
official).

The lower half/16-bit (two 8-bit octets) of the IPv4
LINKLOCAL are generated from the 48-bit MAC address of the
interface.  In IPv6 LINKLOCAL, it is the lower half/64-bit
(four 16-bit words), which easily handles the full 48-bit MAC
address.



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