[ntp:questions] (Software) timeserver for windows being broadcast-able incl. keys

Tom Smith smith at cag.zko.hp.com
Mon Mar 19 21:45:33 UTC 2007

Erik wrote:

> What I do understand is that the difficulty is in the combination of
> broadcast-time-correcting inchangeable
>  (broadcast-)clients on different network segments by one server

It's independent of NTP or anything related to time. The difficulty
is with using broadcast with this network design, regardless of what the
application is. And it's not so much that you have a single server, but
that you have only a single interface that is not on any of the 4 networks
in which you are interested.

> What I still would like to know:
> Is the following (earlier posted) idea...
>> broadcast key 1
>> broadcast key 1
>> broadcast key 1
>> broadcast key 1
> ..from server...
>> IP-adres . . . . . . . . . . . . . . .:
>> Subnetmask . . . . . . . . . . . .:
>> Standaardgateway . . . . . . . .:
> ... definetely useless or still worth a try?

Definitely useless.

> BTW: the manufacturer advises to install its systems in the same
> network segment behind a router to be coupled with the company-VLAN
> The time server, being on the same router, will be able to reach all
> clients by broadcast
> Yet, here we do not have networks-per-manufacturer but mixed networks,
> resulting in a network with systems of this manufacturer
> spread across the whole network (which is divided into several
> subnets)

The key thing to know here is whether each subnet is on its
*own* VLAN or if they are all on the *same* VLAN. If they and
the server are all on the same VLAN, it may be possible
to make broadcast work even with only one server interface.

It may also be possible to make it work if the routers are
configured to route broadcast packets to networks other
than the one they originate on.

If neither of the above is true, which is most likely the case,
I think the only way to make broadcast work would be:

    a) Put a server on each of the 4 subnets. You can peer the
       4 servers together in NTP. In this case, each server would
       broadcast only to its own subnet.


    b) Put 4 NICs in the server you have, and wire each NIC to
       one of the 4 subnets, giving each an address on its own subnet
       instead of the address your server has now. In this case, the one
       server would broadcast to all 4 subnets using the broadcast
       statements you listed above.


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