Dynamic IPs in Pool

Happened to take a look at the source stats on one my client machines that is using the NTP pool, and was surprised to find the PTR record of one of the pool members I was polling indicated it was a DHCP pool residential Internet service IP (specifically a Verizon Fios DHCP residential IP address).


Joining the pool using a dynamic IP address seems to me to be a bad idea as the IP could change at any given time. Some ISPs do not regularly force their customers to a new IP lease (for example, Verizon Fios is commonly known to not regularly force IP lease changes), but a simple power outage or connection issue would lead generally lead to a new IP lease.

Is my thinking wrong? Is this something that has been discussed / decided previously and was decided to be okay?

If not, would it make sense to perform a PTR DNS lookup when someone attempts to add a host to the NTP Pool, and if the PTR contains certain keywords (i.e. pool, dhcp, dyn, dynamic, etc.), not allow the IP to join the pool?

If your IP changes the monitor will lower your score and drops it automatically out of the pool-dns.

Some dynamic-IP’s do not change at all until a power-cut or long disconnect.

You will make it impossible for such users to join the pool.

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It’s hard to tell for sure if a particular IP address is being used as dynamic or fixed allocation.

For example, whatismyipaddress.com is calling the concerned IP address “Likely Static IP”.

Mine is static, it should be able to tell because of my PTR-record.
Doesn’t seem to read those records :smile:

Simple check should be:

bas@workstation:~$ nslookup heppen.be

Non-authoritative answer:
Name: heppen.be

bas@workstation:~$ nslookup name = heppen.be.

Authoritative answers can be found from:


That is a clear indication that it is static.

However, not all ISP’s are willing to give you a personal PTR.