My private router cannot get public IP

[Rinkel]

I have a private Asus router at home, it was getting public IP but it gets private now so the DDNS is not working.  Is ther any policy changed so I cannot get public IP again?  Or it's a problem of my side?

Thanks.

[JimM1]

@Rinkel Going to say at your end, the HTTPS change Asus made going to say 4-8 weeks ago had no effect, and 2 recent FW updates on zenwifi also not affected any change or operation!

Run www.whatismyipaddress.com and if your Asus is set up correctly will return iPv4 and iPv6 addresses.

[Rinkel]

Hi Jim,

 Thank you so much for your reply.  I am using Asus RT-AX58U V2 with custom Merlin ROM.  Let me check again on my router config, though I didn't make any change or firmware update these months, which everything was working without issue. 

Thanks again

[JimM1]

@Rinkel If you search XT8 you will come across my Picture posting's. As you are using Merlin may be another connection that is not giving you a wan IP, you do not say how you have it connected, wan/lan or direct on a FF ONT! I have Asus XT8 direct on the ONT no sky at all connected, back in it's box!

Seems to be the current Merlin but released not that long ago, who knows.

RT-AX58U

3004.388.10_2

[-rpnz-]

Hi @Rinkel 

Are you seeing an IPv4 address from the private RFC 6598 range (100.64.0.0/10), or something else?

If you are, then that is because your Asus router is asking for IPv4 connectivity over IPv6, using MAP-T (RFC 7599), but presumably not actually supporting MAP-T.     We've seen this behaviour with a couple other devices, specifically Ubiquiti Unifi routers, and older versions of OpenWRT, but both of these have been fixed in recent software version.

If you have the option to fully enable MAP-T support, that will help.

e.g., with OpenWRT the MAP package can be installed with: `opkg update; opkg install map`.

But if not, send me a DM and I can forcibly disable MAP-T on your line.

[Rinkel]

Hi rpnz,

No, the ip my wan port assigned is 192.168.0.34

I am using Asus Merlin as rom and siabled ipv6.

Thanks so much for the reply.

[-rpnz-]

Oh apologies then, that's nothing to do with our MAP-T implementation.

That private RFC 1918 address is likely coming from another CPE router in your home that's also running a DHCPv4 server on your LAN.  Do you have a Sky Hub connected as well, or any other device that could be running a DHCPv4 server?

[Rinkel]

Hi rpnz,

No worries, though this is strange that I don't have any DHCP server running in my network. and the WAN port of my router is connecting to the LAN port of Sky Hub.

Thank you so much for the reply again.

[-rpnz-]

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@Rinkel wrote:

the WAN port of my router is connecting to the LAN port of Sky Hub.

---

Oh well then that's certainly where it's coming from.  The Sky Hub does not support bridging mode, so by putting another router behind your Sky Hub router, you've created a double NAT topology, which is not ideal.

[Rinkel]

yeah, i know. but i have better control over my son's internet access, have my vpn service setup to access my private services and apps as well as ddns provided by Asus router.

[Rinkel]

and it was fine weeks ago

[Chrisee]

@Rinkel if you have a Sky hub connected to the line and a second router connected to that there is no way the second router can have access to the public IP address as there is no bridge mode on any Sky hub. If you connect your private router directly to the line which is probably possible then that changes but you lose the Sky c=voice line service.

[-rpnz-]

If all you're worried about is DDNS though, the Sky Hub has a DDNS client built in that you could use, or you can run a client on any host within your network, because they're all sharing the same external IPv4 address.  (IPv6 is different, they will each have their own, but I think you said you've disabled that, and it wouldn't work behind your ASUS router in that topology).

DDNS clients on routers can work in two ways, they can either grab the literal IP address from the WAN interface, which I think you're seeing, or they can probe out to the internet to see what public IP is visible, if behind NAT.  Perhaps your ASUS router has flip-flopped between these two methods recently?  Maybe dynamically, a configuration change, or software update?

Hope that helps, and good luck.

[Rinkel]

Hi folks,

Just an update that I sorted out that the root cause of my initial problem is about the Asus Router Mobile App having kind of configurations override on Router Web UI.

Having a DDNS configuration saved in the mobile app does solve the problem. I am guessing it's related to official Asus mbile app and the Custom non-official ROM. Though this is nothing deal with the private IP, the DDNS service in the custom rom does use external ip checker instead of using WAN ip straight away.

Thanks everyone trying to help me as well as sharing thoughts and possible solutions.