I am trying to access one of my PCs from and external network using RDP on port 3389.

After realizing my ISP uses DS-Lite-Tunnel I gave up ipv4 and focusing on ipv6.

So far the only way I managed to make this work is by:

Activate port forwarding on port 3389 (ipv6 only) on the router; Connect using the ipv6 of my pc network adapter specified as the "IPV6 Address".

My first question would be why do I have to activate port forwarding if the IP I use to connect must be the PC IPV6? I tried to disable port forwarding and then I can no longer connect.

The second question would be why cant I use my public IPV6 number (as shown in whatismyip.com) to connect, if I have port forwarding enabled?

I noticed the IPV6 number on whatismyip is different then the one my router claims to have (the router public ip), maybe because of the ds-lite-tunnel. If I activate on the router a "dyndns" service, the updated ip on dyndns service matchhes the public ip my router claims to have. But I cannot also use my created dyndns domain to make a rdp connection.

My end goal is to connect with the domain name.

Any ideas on how to proceed with that?

  • Unfortunately, questions about home networking are explicitly off-topic here. You could try to ask this question on Super User. – Ron Maupin Jun 16 '19 at 15:10

I am trying to access one of my PCs ...

This seems to be the wrong web site for this kind of questions, because it is only about company networks, not about home networks.

Maybe Super User is more suitable for your question.

My first question would be why do I have to activate port forwarding if the IP I use to connect must be the PC IPV6?

I don't know what the router setting "port forwarding" means in your router:

Most routers have a Firewall that blocks incoming connections for security reasons unless you enable incoming connections to a certain address and port.

Maybe the setting named "port forwarding" actually means: "Allow incoming connections in the firewall".

Theoretically, a router might also perform "real" port forwarding on IPv6 the same way it is done in IPv4:

I know that this is actually done to forward incoming IPv6 connections to IPv4 devices (an IPv6-to-IPv4 port forwarding).

I noticed the IPV6 number on whatismyip is different then the one my router claims to have ...

Please beware that IPv6 works like "classic" IPv4, not like "modern" IPv4:

Using "modern" IPv4 your home network has a public, global IP address (let's say Each computer in your local network has a "local" IPv4 address (for example

Currently, IPv6 works like IPv4 worked 30 years ago:

Every computer in your local network has an own public, global IPv6 address. And (unlike IPv4) it is even possible that a computer uses a different public, global IPv6 address for every single connection!

If you try to connect to the IPv6 address of the router and the "port forwarding" setting of the router actually means "open firewall", the connection will not work, because the router and the PC have different public IPv6 addresses.

There are also different types of "local" addresses in IPv6. But unlike IPv4, the local addresses are only used for connections inside the local network. Unlike IPv4, local addresses are not used for data that is transferred over the internet.


You don't need to connect to "whatismyip" to get the public IPv6 address of the computer. Just just have to take a look at the IPv6 addresses of the computer you are interested in.

Unlike IPv4, a computer typically has multiple IPv6 addresses for each network card!

The IPv6 address(es) starting with a "2" or a "3" is the public IPv6 address.

Example: 2001:db8:123::3:9a7

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  • In my router, port forwarding allows to specify the local ip number, the port number and the protocol for IPv4,IPv6 or both. I am not sure, but I imagine this should be more than simply openning the firewall. After your explanation I would conclude I must leave this port forwarding active more for the firewall openning, since my PC has a public IP number (IPv6) that is public on the internet. But, I would think that my pc should also be reachable by the router IPv6 number, if port forwarding is actually in place. – Igor Kondrasovas Jun 15 '19 at 20:16
  • My idea to use the router IP, is to active the "dyndns" configuration on it so I can access the PC using a domain name. Otherwise, I would have to install some updater in my local pc, correct? – Igor Kondrasovas Jun 15 '19 at 20:16
  • @IgorKondrasovas It is true that the "dyndns" IP address must come from the PC and not from the router if the public IP address of the PC shall be used. – Martin Rosenau Jun 16 '19 at 6:45

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