NTP Sync Issue Across Tata (Europe)

Mon Aug 7 09:36:21 UTC 2023

> So the Anycast address our devices use internally to find the closest
>  NTP server is geo-mapped to MU. 

So indeed, the pool will only send you a single NTP server in this case.
GeoDNS essentially map  you to mu.pool.ntp.org.

You can verify what NTP servers you can expect from the Pool by querying 
it directly (and thus bypassing GeoDNS mappings)

$ dig mu.pool.ntp.org

mu.pool.ntp.org.        62      IN      A       197.224.66.40

> However, the physical server is 
> geo-mapped to the specific countries in Europe, e.g., GB, NL, FR, DE,

What really matters from GeoDNS is the IP address of your client -- the 
one that goes in the NTP query. So if you are using your anycast address 
to query, it does not matter what are the unicast addresses of your servers.

> Unless the geo data ntp.org are using is inconsistent, I'd imagine
> the servers should be mapped to a European pool, since the physical
> address from which the server queries the pool is geo-mapped locally,
> for this specific reason.

They also use the latest Maxmind mappings, and I confirmed it 
experimentally. ( I think it's fully automated their update method)

/giovane