NTP question

Stephen Satchell list at satchell.net
Thu May 2 01:21:04 UTC 2019

One word of caution when using a low-priced NTP appliance: your network
activity could overwhelm the TCP/IP stack of the poor thing, especially
if you want to sync your entire shop to it.  In the case of the networks
I set up, I set up a VLAN specific to the NTP appliance and to the two
servers that sync up with it.  Everything else in the network is
configured to talk to the two servers, but NOT on the three-device "NTP
Appliance VLAN".

NOTE: Don't depend on the appliance to provide VLAN capability; use a
configuration in a connected switch.  How you wire from the appliance to
a port on your network leaves you with a lot of options to reach a
window with good satellite visibility, as CAT 5 at 10 megabits/s can
extend a long way successfully.  Watch your cable dress, particularly
splices and runs against metal. (Or through rooms with MRI machines --
I'm not joking.)

The two servers in question also sync up with NTP servers in the cloud
using whatever baseband or VLANs (other than the "NTP VLAN") you
configure.  Ditto clients using the two servers as time sources.

The goal here is to minimize the amount of traffic in the "NTP Appliance
VLAN".  What killed one installation I did was the huge amount of ARP
traffic that the appliance had to discard; it wasn't up to the deluge.

Learn from my mistakes.

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