IPv6 vs IPX

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In a session last week came the following comment from a presenter (paraphrased):
How may of you in the room have been at this long enough to do IPX? Ok, great. Now how many of you have done anything with IPv6? Doesn't that look JUST like IPX?
And he's right, to a point. IPX addresses are of the form network-number:node-number, such as:

00008021:0002a540d0e1

Where 'node number' is the MAC address of the network card in question. It's up to the routers to figure out where network-numbers live, and advertised services issue full-network broadcasts to advertise said service, which is the primary reason that IPX just doesn't scale if WAN links are in the mix. But that's by the by.

IPv6 addresses work similarly:

2001:0db8:85a3:08d3:1319:8a2e:0370:7334

The last 48 bits are the MAC address and the bits ahead of it constitute the network number. Except... the IPv6 designers knew about the failings of IPX and worked around them. The last 48 bits don't have to be the MAC address, though as I understand it that address has to exist for each physical interface. Unlike IPX, IPv6 has the ability to have 'secondary' addresses. The lack of this ability was the main reason that Novell Cluster Services only worked on IP networks, which caused its own wave of grief when clustering was introduced in the NetWare 5.1 era. Secondary IPv6 numbers don't have to follow the MAC format, which in my opinion is a good thing!

Yes, when I first read about IPv6 addressing I had that same, "wow, this is just like IPX," moment the BrainShare presenter had. Only, more scalable, and more flexible.

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