IPv6 address and routed /64

[Mijzelf]

Yesterday I applied for a HE IPv6 tunnel, and got one. The default tunnel consists of an IPv6 address, ending on ::2, and a routed /64 subnet. What struck me is that the address is in a different /48 subnet than the routed /64 subnet. That means that a whole /48 subnet is burned just to provide my router an IPv6 address.

As my former Sixxs IPv6 address and subnet had the same peculiarity, I guess there is a technical reason for that. Which one?

[cholzhauer]

Yesterday I applied for a HE IPv6 tunnel, and got one. The default tunnel consists of an IPv6 address, ending on ::2, and a routed /64 subnet. What struck me is that the address is in a different /48 subnet than the routed /64 subnet. That means that a whole /48 subnet is burned just to provide my router an IPv6 address.

I don't understand that, can you elaborate?  If your tunnel /64 is 2001:db8:1234:4567::/64, mine can be 2001:db8:1234:4568::/64.

[Mijzelf]

My IP is A:B:C:D::2/128, while the routed /64 is A:B:E:F::/64 .

And you are right, others IP could be A:B:C:G::2/128, or even A:B:C:D:H::2/128, although the latter is becoming inconvenient.quickly. So I guess the /48 subnet could provide 64k single endpoints.

So I think my real question is: Why is my endpoint IPv6 address not inside my routed /64 subnet?

[divad27182]

Yesterday I applied for a HE IPv6 tunnel, and got one. The default tunnel consists of an IPv6 address, ending on ::2, and a routed /64 subnet. What struck me is that the address is in a different /48 subnet than the routed /64 subnet. That means that a whole /48 subnet is burned just to provide my router an IPv6 address.

As my former Sixxs IPv6 address and subnet had the same peculiarity, I guess there is a technical reason for that. Which one?

Not quite right.

You got A:B:C:D::2/64 for your router, and A:B:E:D::/64 as your subnet. 

This means there is a /64 for your router to their router communication, and a /64 for your use.  And then, presumably, each tunnel through that HE node gets is own unique D value, and shares the A:B:C:: and A:B:E:: subnets.

Admittedly, it might have been a better use of resources to give out A:B:C:0:0:0:D:2/112 for the router and A:B:C:D::/64 for the subnet, but it's probably better just not to try to explain using /112 (or even /126 or /127) subnets.

--David

[divad27182]

My IP is A:B:C:D::2/128, while the routed /64 is A:B:E:F::/64 .

And you are right, others IP could be A:B:C:G::2/128, or even A:B:C:D:H::2/128, although the latter is becoming inconvenient.quickly. So I guess the /48 subnet could provide 64k single endpoints.

So I think my real question is: Why is my endpoint IPv6 address not inside my routed /64 subnet?

Actually, that can be done, but it requires such painful routing rules on both ends that it isn't worth doing.  The issue is that their router's endpoint IPv6 address would then also need to be in your routed /64 subnet, but would not be truly in that subnet.  As I said, painful routing rules.

--David