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So, my SiXXS' POP seems to be in trouble and I was thinking in changing to HE. The idea is connect to HE, change radvd setup and... lots of other thinks:

  • UFW, specially in laptops, which only allows access to some development services from some RFC1918 addresses and to my global IPV6 addresses

  • My servers have fixed IPv6 addresses to easily DNS setup

  • Some software needs some type of reference to the "local" addresses in setup (like squid acls or libvirt networks)

  • etc.

So my question is: what is the best way to deal with this?, let's suppose that tomorrow I need to change my tunnel broker, or for whatever reason I need to change my prefix and use another provider as a backup, do I really need to review all my setup? The only solution I can think of is ULAs and NAT which I dislike (or ULAs plus global addresses but I think this setup is not recommended)

(A possible solution if I understand correctly would be Mobile IPv6, but is this really an option today?, how many providers work with it?)

Summarizing: what options do I have to simplify the administrative task of changing IPv6 prefix of a network?


Thank you very much for your answers but I think that I have left some things unexplained that are important for this question: https://en.wikipedia.org/wiki/IPv6_address#Default_address_selection gives a table of the selection preference in case you have more than one address. As both SiXXS and HE use 2001:: prefixes, this means that (if I read the table correctly) the global addresses will always be selected and never the ULAs. So if I setup squid to limit access based on ULAs, it will not work because all clients will identify themselves with the global address. There's another question about the same issue but the answer, using both ULAs and global addresses works because the public prefix is 2000:: in this case.

I am right?, or I'm wrong about address preference?

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2 Answers 2

Mobile IP is not for situations like this. It is for when you take devices from their home network to another network but you still want them to use their original address. The home network must be reachable though.

For services that only need to be reachable from your own networks you can use ULA for stable addressing. You can use ULA side by side with glibal addresses to have both stable internal addresses and global connectivity. You'll need to manage two prefixes per network so it might be a bit of extra work.

And for global addresses: yes, if you switch from one ISP to another then you'll need to renumber everything.

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ULA (FD00::/8) could have been leveraged in setting this up to simplify things. You can set up /64 prefixes within it as you see fit (SiXXS maintains a registry, in case you're concerned about assuring your ability to route someone else's ULA prefixes), and deploy (encrypted) VPNs to connect them. Then, your security-critical services can accept traffic only from FE80::/10, FC00::/7, and ::1/128, and they won't be directly exposed to the internet. These addresses would be the rough equivalent of listening only on loopback and RFC1918 addresses (though FE80::/10 is actually more like APIPA,

If you're going to renumber, which you should (you absolutely must not continue using addresses from your SiXXS assignment if you relinquish it, as they would then be bogons and you would risk interoperability issues), you should renumber those services into ULA. Then, you will not have to renumber these local things next time you change providers. There is no need for NAT in this case, because every host can have many addresses (eg. a link-local, ULA, and internet address, or a few of each). Far from being not recommended, this is exactly what you are supposed to do.

The idea with IPv6 is that every host has lots of addresses and can use them for the appropriate purpose. Leverage this.

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Site-local addresses don't exist anymore. They have been deprecated in favour of ULA. Please don't tell people to use them. –  Sander Steffann Feb 10 '13 at 20:14
Hmm, you're right. How did I not notice that? –  Falcon Momot Feb 10 '13 at 20:25
Thanks for adjusting the answer! –  Sander Steffann Feb 10 '13 at 23:30
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