[ixpmanager] Trouble adding v6 /64

[Nick Hilliard]

Nishal Goburdhan wrote:
> ie, when you apply for your next block of IPv4 addresses for your
> peering lan, at afrinic, you won’t be getting addresses assigned from
> 196.223.x, but from 196.60.y.   so the “consistency” that you are aiming
> for, would be unrealised in the future.  unless, of course, you plan to
> change your IPv6 addresses at the same time - and that’s a totally
> unnecessary pain.

Agreed that explicitly tying the IPv6 address to the exact ipv4 address
is something that will bite in future years.  We had several iterations
of IPv6 addressing at INEX before we realised that there was no
compelling argument to encode information of any form in ipv6 addresses,
and that doing so would invariable cause problems down the line where
the terms for encoding the information changed, but there wasn't a
compelling reason to renumber the ipv6 address.

In other words, the for anything other than simplest: start off at
address number 0 and increment.  We eventually decided to make the
decimal representation  of the last ipv4 octet the same as the hex
representation of the last octet in ipv6, i.e.

186.6.36.6 - 2001:7f8:18::6
186.6.36.150 - 2001:7f8:18::150

We considered plenty of other schemas along the way (e.g. ipv4 address
mapping, ASN encoding, and curiously a scheme which guaranteed that each
IPv6 address would end up in a different multicast group for ND
announcements (long story, but there were some nasty bugs in the early
days of Cisco 6500 kit, ouch)).

Obviously, each IXP is different, and you can do whatever you want from
the UI in 4.7.0.

The only encoding that INEX uses in either IPv4 or IPv6 is to reserve
all single-digit addresses for IXP use only (and we didn't even succeed
at this, oops).

Nick