Troubleshoot IPv6 Issues

From ARIN IPv6 Wiki

Use this page to collect tips on how to troubleshoot IPv6 issues. For instance, adding an AAAA record for a service to your DNS will result in some people losing connectivity and others experiencing unusually high latency. The root cause for connectivity loss is usually that the end user is on another network with IPv6 on their PC but no form of IPv6 connectivity. In fact, their company may be blocking Teredo and 6to4 traffic. The root cause for high latency is usually that the end user is using some form of tunnel (ISATAP, tunnel broker, 6to4, Teredo) that causes their traffic to trombone out to a distant tunnel endpoint and then come back again, or perhaps the tunnel endpoint is on a network that has poor IPv6 connectivity.

As you deploy IPv6 and as other networks deploy IPv6, your helpdesk will see new and different problems. Also, problems that seem familiar will turn out to have different root causes from before. You will need to deal with this issue even if you are delaying implementation of IPv6 in your own network.

In order to debug connectivity issues, you can easily traceroute from various places to your network by setting up an IPv4-only host and setting up various kinds of transition technologies on it (6to4, Teredo, Hexago and SixXS tunnels, etc.)

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It may not be initially obvious, but your IPv6 throughput may not be the same as your IPv4 throughput.

Service providers may have IPv6 transit or peering, but those connections may not be dual-stacked and so IPv6 operates over a separate physical interface than the IPv4 traffic.
The IPv6 path is more circuitous than IPv4 because of sub-optimized routes to get to the target node. Because there are so (comparatively) few IPv6 links, the physical path to the target mode may be indirect.
The service provider may have less-optimized transit or peering links than IPv4, and so while they may have IPv4 peering with Company A and B, they may not have IPv6 peering with Company B.
An intermediate router(s) may not be able to route IPv6 in hardware but only in software, and relatively low levels of traffic may bring the router to a very high level of CPU utilization resulting in lower IPv6 throughput.
The service provider may be using tunnelling or 6to4.

In addition to their service provider's topology, an end-users' local IPv6 environment may result in poor IPv6 throughput.

The end-user's PC could be using Teredo and all the traffic is being tunneled through a remote host positioned sub-optimally in the path to the target node.
The end-user's router tunnels to a remote host that is also not in the path to the target node.
The end-user's router is performing IPv6to4 and the network stack is not well-optimized.

The only way to know what the performance of your IPv6 link is to perform a real IPv6-based test.

Here are some IPv6 "speed test" sites: