[systemd-devel] Antw: [EXT] Re: network-online.target time

[Peter Morrow]

On Thu, 2020-05-07 at 08:57 +0200, Ulrich Windl wrote:
> > > > Peter Morrow <
> > > > Peter.Morrow at microsoft.com
> > > > > schrieb am 06.05.2020 um 17:56
> 
> in
> Nachricht
> <21624_1588780597_5EB2DE35_21624_6_1_aa19cc55fd1846a2344357bfb5465a64
> 5993bf1a.ca
> el at microsoft.com
> >:
> [...]
> > > You can turn that off if you like: IPv6DuplicateAddressDetection=
> > 
> > This option worked well when I tried it (total time came down to
> > ~700ms) but unfortunately disabling it entirely isn't an option.
> > 
> > FWIW setting CONFIG_IPV6_OPTIMISTIC_DAD=y in the kernel is
> > providing a
> > good middle ground.
> 
> As a note from real life: A major IT company claiming to be the
> horsepower for
> enterprises, (so to say) once sent out a replacement motherboard for
> a
> defective server, and when we powered up that server again, a storage
> system
> from the same company failed. As it turned out the new motherboard
> had the same
> MAC address as that storage system's NIC...
> When the technician suggested to replace the server motherboard
> again, I was
> asking whether it wouldn't be easier for all if the MAC address would
> be
> re-programmed. The technician said that it's impossible to change the
> MAC
> addresses... ;-)
> 
> Long story put short: Tests for duplicate addresses DO make sense....

Absolutely!  In fact in a previous life I've written software to
program MAC addresses into EEPROMs (given some input list of addresses)
and have seen first hand similar problems to the one you describe :)

Thus disabling DAD altogether is not an option.

Cheers,
Peter.


> 
> > Peter.
> > 
> > 
> > > Lennart
> > > 
> > > ‑‑
> > > Lennart Poettering, Berlin
> > 
> > 
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