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Migrating Applications to IPv6 by Dan York

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Chapter 6. Documentation, Training, and Testing

While the bulk of this book has been focused on your application itself, three areas that complement your application also need to be considered: documentation, training, and testing.

Documentation

When you write documentation for your application (you are writing documentation, aren’t you?), what IPv6 addresses are you using in your examples?

If you just use a random IPv6 address, it could turn out to be someone’s real IPv6 address. Even with the IPv6 address space being so huge, there still is the remote chance that your documentation choice could collide with a real address and potentially cause traffic or routing issues. If you use your own IPv6 addresses, well, are you sure you want the traffic of people typing in examples and hitting your systems? (And maybe I’m personally just too concerned about security, but I don’t want to have people probing around my systems!)

Thankfully, the good folks at the IETF solved this issue for us with RFC 3849, IPv6 Address Prefix Reserved for Documentation. The magic IPv6 address prefix to use for documentation is:

2001:db8::/32

That prefix has been permanently allocated for documentation purposes and will never be assigned to an actual end party. It is, as they say, “nonroutable.”

If you look at the IPv6 addresses I have been using throughout this book, you’ll see that they all use the 2001:db8: prefix, although with various lengths:

2001:db8::1
2001:db8:10ff::ae:44f2
2001:db8:1212:3434:1212:5454:1afc:4001 ...

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