Why Does IPv6 Traffic Take Different Path From IPv4 Traffic?

A common misunderstanding is assuming that IPv6 traffic will take the same route as Ipv4 traffic. Even when the source and destination address is the same, the two protocols might take divergent paths.

It's normal for IPv6 and IPv4 to travel through different networks. Different routes for reaching the same destination do not indicate a problem.

The reason for this is that IPv4 and IPv6 peering is not always the same. A lot of networks have totally different policies when it comes to their own IPv6 and IPv4 traffic. Certain networks are happy to peer with anyone over IPv6, but are more selective when it comes to IPv4 peering.

Some networks peer directly with one another over IPv4 but not over IPv6.

What this means is that the IPv6 Internet looks different than the IPv4 Internet. The same paths will not be available in both protocols. This is OK. It just means that some networks have different policies when it comes to IPv6 and IPv4.

Not only that, but some networks will peer for free over IPv6, but not over IPv4. What this means is that two networks might have a connection over IPv4 and IPv6, but because IPv6 traffic is freely exchanged between them, they are happy to send IPv6 traffic directly to one another. IPv4 traffic might then be paid, and it might be cheaper to send IPv4 traffic in a more roundabout way, through a third network that has cheaper rates for IPv4 traffic.

So in conclusion, sometimes IPv4 and IPv6 traffic will travel in different ways. This does not mean there is anything wrong, it just means that the networks that the traffic is going through have different policies based on the two protocols.

If you see large performance issues between IPv6 and IPv4 you can try to contact your Internet service provider and hope that they can more closely align their IPv4 and IPv6 policies.