Dynamic DNS - dynu.com ipv6 ipv4 wrong IP updating!

Installing and Using OpenWrt
1

my settings:

lookup hostname: xxx.dynu.net
IP address version: IPv4-Address

well everything else just as should be..

what do I expect, to dynu.net get my IPv4 address right?

Instead, it also updates the IPv6, but the WRONG !!

I told it to take the IPv4 from the pppoe interface, which it does great, it get's the ipv4 from the pppoe and updates.

BUT,
the pppoe also has a pppoe- virtual dynamic iunterface DHCPv6 which gets a IPv6.

Now, it would be RIGHT if the dynamic update would detect this IPv6 and update dynu.com
with this IPv6 address, but it doesn't!

Instead, it goes looking at the LAN, the br-lan, and see which IPv6 address the br-lan has and picks the br-lan ipv6 and this is the IP it's updating the dynu.com service with.

That's totally weird, wrong and I think it's a bug. Because when you tell explicit ipv4 I wouldn't expect it to update the ipv6 anyway, but even if it does, why wouldn't it pick the IPv6 from the pppoe but instead picks the IPv6 from the br-lan?

2

It is not a bug.

In IPv6 you get one subnet for the wan link between your router and the router of the ISP, as well as one delegated prefix to use in your lan. Sometimes the ISPs block the access to the wan subnet from the internet, hence it makes sense to advertise only the lan IPv6 address.

You can test yourself which address is used:

wget https://ipv6.icanhazip.com/
cat index.html

You'll see that the lan address is used.

3

Well I think it's a bug, or at least a failure in documentation but I think sincerely it's a bug.

Reason: dynu replied to me that I need to add myipv6=no

so the complete URL would be:
https://api.dynu.com/nic/update?hostname=[DOMAIN]&myip=[IP]&myipv6=no&password=[PASSWORD]

setting ipv4 in LUCI as the IP to be updated, picks the IPv4 from the WAN, but doesn't add the "&myipv6=no"
in the updating command and thus the api of dynu adds "first IPv6 it finds" according to the dynu support.

So openWRT should include the "&myipv6=no" if the user selects the IPv4 option.

btw manually adding the "myipv6=no" into the /etc/ddns/services seems to work and indeed prevents the IPv6 from being updated by the ipv4 command.

4

You can simply disable IPv6 on WAN.

Why would OpenWrt add that argument to the URL?

Then those with working IPv6 cannot use DDNS. The value myipv6=no is on the Dynu server, how would this be an OpenWrt bug?

5

"You can simply disable IPv6 on WAN."

For starters, I want IPv4 and IPv6 on my WAN :slight_smile:

"Why would OpenWrt add that argument to the URL?"
ehm, because it works?

"The value myipv6=no is on the Dynu server, how would this be an OpenWrt bug?"
because it needs to be used in the openWRT servives line for that service and not on the server?

AGAIN, if I in openWRT select the Ipv6 for dynu.com, the correct IPv6 from the WAN is uploaded!

If I select to also update the ipv4 for dynu.com, the wrong IPv6 from the LAN is uploaded and this can be prevented by adding myipv6=no into the services line of openWRT and use another, a 2nd ddns updater, to actually update the IPv6 with the WAN Ipv6

But yeah you're right, the real bug is probably why does openWRT detect the LAN IPv6 instead of the WAN Ipv6, when selecting to update the IPv4

6

I agree that IPv6 DDNS needs some custom configs if you want it to point to a downstream IP.

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7

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