Re: NTp config - for the databases :}

[kees () echelon nl (Kees Hendrikse)]

> > time by spoofing only **one** of your 18 reference servers. NTP will happily
> > follow this one phoney server, as long as it believes the other 17 are dead. 
> > I don't even have to be careful with time changes. Now that the phoney server
> > is the only reference, NTP will follow it all the way.
>
> That catch is that the stratum2s are also peering to each other, so unless
> your spoofed reference is more stable than the combined clock of the three
> they will ignore it.

I'm sorry, but you're wrong. 
You are left with only *one* stratum-2 system; the others will drop to
stratum-3 or lower by lack of a stratum-1 reference. These stratum-3
systems peer to each other and use your only stratum-2 left as there
single point of reference. 

Try it. Block all incoming ntp-traffic except the traffic from one of the
external servers. You might be surprised as to how quickly ntp adapts. 

-- 
Kees Hendrikse                               | email:     kees () echelon nl
                                             | web:        www.echelon.nl
ECHELON consultancy and software development | phone: +31 (0)53 48 36 585
PO Box 545, 7500AM Enschede, The Netherlands | fax:   +31 (0)53 43 36 222