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DDNS updating as a cron job?

Started by kjalger, December 31, 2023, 03:38:27 AM

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Background:  My ISP is BT(UK) and very occasionally my IPv6 address changes all on its own.  As my Asus router seems to monitor ppp0 for updates and my IPv6 WAN/Gateway address doesn't appear there, an updated IPv6 address on its own does not fire the DDNS update script!
For the moment I've set the DDNS forced update to once per day (21 days by default) just using the router WebUI (simplest way - and it's a rare event).  But I have considered (and very briefly did) set the router ddns-start script to fire regularly using a cron job.
I'm very appreciative of HE providing this service at no cost to users, and don't want to fall foul of abusing the service.  So I wondered what the guidance on how often it is sensible to fire off a ddns update?


The Linux/Unix pppd program has a hook at file "/etc/ppp/ipv6-up".  Maybe this is also called when the IPv6 address changes, as opposed to interface up only.  Your router's version of ppp May have something similar....


re: guidance - i saw this


it seems the limit is every few minutes.

they didn't list examples of well behaved scripts, but it seems there might exist scripts for your router if you google around?



I wouldn't say the limit is "every few minutes", but "when your IP changes."

We'll accept an attempt to request an update, regardless of it is an actual change, and not block it every few minutes, but the goal is to request an update only when you need to.

At least 90% of the updates we see are unneeded, or entirely malformed requests because people put their information in the wrong fields (passwords as tunnel IDs, etc.), and then never test their setup, so it runs that way for years.