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Re: IPv6 Interview Questions and critic

  • From: Peter John Hill
  • Date: Tue Aug 27 14:45:58 2002

On Tuesday, August 27, 2002, at 10:41  AM, Joe Baptista wrote:

Ipv6 uses 128 bits to provide addressing, routing and identification
information on a computer. The 128-bits are divided into the left-64 and
the right-64. Ipv6 uses the right 64 bits to store an IEEE defined global
identifier (EUI64). This identifier is composed of company id value
assigned to a manufacturer by the IEEE Registration Authority. The 64-bit
identifier is a concatenation of the 24-bit company_id value and a 40-bit
extension identifier assigned by the organization with that company_id
assignment. The 48-bit MAC address of your network interface card is also
used to make up the EUI64.
Since it so easy for a host (relative to ipv4) to have multiple ip addresses, I like what Microsoft has done. If told by a router, a Win XP box will assign itself a global unicast address using EUI-64. It will also create a global unicast anonymous address. This will not be tied to the hardware, and the OS will also limit how long it uses that address before deprecating that address and creating a new preferred anonymous address. I can see servers using the EUI-64 address, while clients use the anonymous address. It will allow servers to narrow down who is accessing their servers to a 64 bit subnet. That will be good enough for most statistics, but will make it more difficult to do the scarier tracking of users.

I have noticed that the Linux and Mac OS X ipv6 implementations so not create the private addresses automatically.
Peter Hill
Network Engineer
Carnegie Mellon University

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