Does load-balancing make sense for NTP?

I’m planning to setup an NTP service in my lab, and joining it to the pool for public access. My plan is to run an internal/private Statum 1 appliance with a GPS sync, and then below that add one or more stratum 2 servers in my DMZ to join the pool. However, as I only have 1 public IP address, I cannot expose more than one of these directly to the public. One possible solution would be to add a load-balancer in front of the several stratum 2 servers, which would increase availability, but As the various stratum 2 servers are not 100% in sync, I’m wondering, if load-balancing between several tightly syncronized stratum 2 servers would actually do more harm than good?

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How would you ensure that the same client always arrives at the same server?

TL;DR: Your instincts are right. Load balancing NTP doesn’t make sense, and can do more harm than good.

RFC8633 (NTP Best Current Practice) has a section on anycast, and the same considerations apply to load balancers.

If you have only one public IP address, expose just one stratum 2 server to the pool.


If your main goal is availability, you can use your load balancer’s failover mechanisms to only send traffic to one server at a time.

Previous thread on this: Thinking of joining, is load balancing okay?

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