I am trying to implement Dual Stack configuration of a network in Packet Tracer. I have two routers connected to each other both of these routers have one IPv4 client and one IPv6 client. The routers are configured to use both IPv4 and IPv6 protocols. I am able to send packet from one IPv4 client to another IPv4 client via both the routers. Similarly its also working for IPv6 clients.

I am unable to send packet from an IPv4 client to an IPv6 client via both the routers and vice versa.

Is this kind of communication between IPv4 and IPv6 is possible using only Dual Stack? If yes kindly help me with the problem.

Thanks in Advance.:)

Below given is the link to the network we designed.

network diagram

  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Aug 10, 2017 at 4:51

4 Answers 4


Dual stack means that an interface can communicate with both v4 and v6 clients. It DOES NOT mean that it will translate between the two. For that, you need to implement NAT-PT, to translate between the different layer 3 protocols. BTW, I've never seen NAT-PT work at any scale.

  • You weren't the only one who noticed NAT-PT has issues, it has been deprecated (see RFC 4966).
    – Gerben
    Jul 16, 2014 at 22:27

In a dual stack network, a host has both an IPv4 and an IPv6 configuration allowing them to choose which protocol to use. When communicating with an IPv6 host, it will use its IPv6 address, when talking to an IPv4 host, it will use its IPv4 address.

From your question, I gather that you have IPv4 on all systems, but IPv6 is only configured on the routers. To make the network fully dual stack, the hosts should also be configured to run IPv6.

To allow an IPv4-only host to an IPv6-only one requires some kind of address translation. There are different so-called "IPv6 transition mechanisms". Most are designed to be able to deploy IPv6-only networks and still allow the machines to talk to IPv4 networks.


In addition to Gerben answer:

IPv4 and IPv6 are to different protocols. So a IPv4 only client can only communicate with an IPv4 server. An IPv6 only client can only communicate with an IPv6 Server. Dual-Stacking means that you uses both protocols. Most modern operating systems will then prefer IPv6 over IPv4.

There are some ways to "translate" one protocol into another, for HTTP (and some others) you can use a proxy server. For a wider variety of protocols NAT64 / DNS64 works pretty well unless you (or the party you are trying to communicate with) uses IP addresses (e.g. to embedded pictures into a web page) instead of DNS. AFAIK for Cisco the NAT64 part can only be done on ASR1K routers.

Please forget everything you read about NAT-PT which is deprecated but might still be used for some (Cisco) certification tests.


The combination of DNS64 / NAT64 works well for solving the problem of IPv6 hosts reaching IPv4 hosts outside their own network.

The BIND and Unbound DNS servers implement DNS64 for free. You can get NAT64 for free from OpenBSD 6.4, or go commercial and buy a firewall from Cisco or PaloAlto.

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