Don't disable IPv6!
Although it's taken a long time for the adoption of IPv6 to get going, it isn't a good idea to disable this network stack for the sake of convenience. After all, much of the IPv6 infrastructure is now in place and is extensively used. And disabling IPv6 can actually cause problems.
Migration to IPv6 has only really got going in the last couple of years. Nevertheless, Google stats show that about a quarter of visitors now reach the company's sites using IPv6.
However, the slow early pace of IPv6 adoption means that interest in the topic has waned. System managers are no longer asking their network colleagues for it. Network managers are no longer asking their internet and hosting/colo providers for it. And end users aren't asking their access providers for it. Because IPv6 currently co-exists alongside IPv4 as a parallel network, there is also a risk of an IPv6 infrastructure that was set up earlier falling into disuse, perhaps unnoticed.
'Prefer IPv4 over IPv6'
As a result, it's not unusual for a connection to a dual-stack system to take a while to come up, due to an issue with the intermediate IPv6 network. There's then a delay before the system tries again using IPv4. You'll therefore often hear it suggested that the best thing to do is disable IPv6. However, that advice is misguided. If you can't find an answer to your IPv6 problems, or the solution is in someone else's hands, what you should do is change your client's network setting. Instead of the common 'Prefer IPv6 over IPv4' default setting, switch to 'Prefer IPv4 over IPv6'. The rationale for that is explained in this Cisco blog post. Cisco says that disabling IPv6 is treating the symptom, not the disease: the underlying network problem remains unresolved.
Microsoft also warns against disabling IPv6. You may remove your acute problem, but you're letting yourself in for much bigger problems further down the line. The reason being that IPv6 is integral to the Windows operating system. Consequently, applications are not tested in situations where IPv6 is disabled. In the face of insoluble problems, Microsoft advises enabling the 'Prefer IPv4 over IPv6' option.
We're currently in the midst of transition from IPv4 to IPv6. While that transition is in progress, running a dual-stack IPv4/IPv6 set-up on a network infrastructure is temporarily unavoidable. Anyone who remains in doubt should bear in mind that the Netherlands is lagging a long way behind on IPv6 adoption [1, 2]. Consequently, people around you may be less inclined to prioritise IPv6 than their counterparts elsewhere. Meanwhile, however, the rest of the world is migrating fast.
And, in an international environment — which the internet obviously is — you can't afford to stick with an outmoded, incomplete connection. Don't forget that the annoying delay you're experiencing because of someone else's poor IPv6 set-up is exactly what others will experience if your network isn't configured correctly or doesn't support all the options. Last month, Infoblox published a blog post emphasising the reciprocal nature of a (business) internet connection: Things are fine for the companies that don't support IPv6 on the grounds that their IPv4 address stocks or NAT set-ups cover their needs. It's their customers, partners and suppliers with no IPv4 addresses left who encounter the problems.
The sooner we all switch over, the sooner we'll all be rid of the problems and expense associated with the current situation. And the sooner we can all enjoy the fruits of a fully symmetrical internet.