DDNS support from FQDN


#1

Is there any way to have the FQDN update the IP address periodically? I’m using DDNS for one of my servers and when the address changes I have to go in and delete the old server and create a new one in the pool. Not too complicated or hard but it would be nice if it was more automated.

Thanks.


#2

No, there isn’t. http://www.pool.ntp.org/en/join.html says: “Your computer must have a static IP address and a permanent internet connection. It’s very imporant[sic] that your IP address doesn’t change or only does so extremely infrequently (say once a year or less).”


#3

The pool server management page does allow input of hostname, but it will only do a one-time lookup for the (supposed to be) static IP address. Theoretically the pool can emit short lived CNAME to DDNS hostname, then further resolve to your actual dynamic A address, but it will cause unnecessary burden to DNS infrastructure and will not likely be implemented.


#4

FWIW my stratum 1 is on an ip that is, in theory, dynamic. However my ISP hasn’t changed it in over 2 years so I feel comfortable using it.


#5

you could write a bot using linux curl command to delete the IP address and add the new one, however for joining the NTP pool it is a requirement for quality purposes the server has static IP address.


#6

The bigger problem is that many of our clients are daemons that just do a single DNS lookup and then run for many days, weeks or even months.

In the future I’d like to have a way to service users differently if we know which client type they are (SNTP vs NTP) based on the zone name they use. For “SNTP clients” we could allow for servers that have more dynamic IPs.


#7

Allowing servers with dynamic IP addresses would be a very nice feature. I think there are actually three classes of clients:

  1. DNS lookup only on start
  2. DNS lookup on start and when a server becomes unreachable, falseticker, etc.
  3. DNS lookup before each NTP request

Class 3 has only SNTP clients. In class 1 and 2 are both NTP and SNTP implementations and it may also depend on their configuration (e.g. ntp-4.2.8 configured with the pool directive instead of server).

Servers with dynamic IP could serve class 3 and probably also 2.


#8

My address is dynamic but as long as I keep using it it will basically be static. I had used the same one for years but I started having issues with Akamai blacklisting me because I also run a Tor relay at the same address. I could get unblacklisted by changing my MAC address and getting issued a new IP address. That would work for an hour or so and I’d get blacklisted again. I’m taking the Tor relay down as it’s not worth the headache of getting a bunch of content blocked. So my address should be statically dynamic again.