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Accepted
Jacob Evans
Asked: 2017-08-01 08:07:31 +0800 CST

What is the best default-gateway for IPv6

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Since IPv4 private IP Space was never contiguous, it is typical to send all unknown routes to an upstream gateway, such as your internet provider (ISP).

With IPv6, private IP space is contiguous, and only 2000::/3 has been assigned as internet addressable by IANA

Would it be better to only route 2000::/3 to the ISP as opposed to all assigning a default route. (or use RA)

I would say it is obvious that all unregistered IP addresses are blocked from going out the wan (RFC1918,RFC5735, etc) so questions related to firewall/security are out of scope. This question is restricted to ROUTING please.

routing

1 Answers

  1. Best Answer

    Would it be better to only route 2000::/3 to the ISP as opposed to all assigning a default route.

    No. While Informational RFC 3587 is not a standard, it offers the following advice:

       RFC 2374 was the definition of addresses for Format Prefix 001
   (2000::/3) which is formally made historic by this document.  Even
   though currently only 2000::/3 is being delegated by the IANA,
   implementations should not make any assumptions about 2000::/3 being
   special.  In the future, the IANA might be directed to delegate
   currently unassigned portions of the IPv6 address space for the
   purpose of Global Unicast as well.

    If you wanted to do this for a personal device, that's your own business. Given that this question is being asked on Serverfault and a business IT scope is assumed, the answer would have to be an unequivocal no. Any production environments designed around this assumption would have to be revisited at a future date if IANA assigns more of the address space to a purpose of Global Unicast. The design would also violate the design principle of least astonishment as it would not be reasonably expected of any future employees who are familiar with IPv6.

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