ietf
[Top] [All Lists]

Re: IPv6 addressing limitations (was "national security")

2003-12-02 13:58:03
On 2-dec-03, at 20:42, Schiro, Dan wrote:

Fortunately  the mistake is easily rectified, so long
as software doesn't get into the habit  of expecting the lower 64 bits
of an address to be a unique interface identifier.

This is a dangerous prospect. The company I work for makes a networking stack and our IPv6 implementation expects the lower 64 bits to be the unique
interface identifier.  Other implementations do the same.

Interface identifiers aren't required to be unique. Anyone who expects them to be be in trouble at some point. There are many ways in which the same interface identifier can show up in more than one subnet:

- manual configuration (interface identifier 02-00-00-00-00-00-00-01 is very popular)
- RFC 3041 and a whole lot of bad luck
- there are systems on the market that use the same MAC address on more than one interface - there have been many screwups with MAC address assignment during production

But what benefit is there to assuming that interface identifiers are unique anyway?