IPv6 site local EUI-64 adresses and jails

David Malone dwmalone at maths.tcd.ie
Sat Aug 13 08:53:06 GMT 2005

On Fri, Aug 12, 2005 at 08:53:20PM +0200, Emanuel Strobl wrote:
> Now in the 24-16-24 scheme of th interface id part of the IPv6 address, the 
> 16 bits were inserted with the value FFFE. And bit 57 was changed to one! 
> Why???? What if it is alread one? Or isn't tehre any vendor who can have 
> bit 41 of his MAC 1?

Some of the bits of a MAC address are reserved. There is a bit that
indicates if the address is the address of a group of machines (for
multicast) or the address of a single machine. The bit that is
flipped when generating IPv6 addresses is the "local/global" bit,
that indicates if the address has been assigned locally or by some
global authority.  For normal ethernet cards, this bit would always
be 0.

> Now I want to use a dedicated interface, which is in a different subnet, 
> for 5 jails. How do I do that if I want to keep the MAC relation and if 
> I'm not allewd to change the FFFE insert? It isn't possible then, is it?
> What should I do instead? Invent my own 64-bit scheme?

I'd suggest that you use manually assigned addresses in cases like this.
You know what sort of addresses will be generated by autoconfiguration,
so it should be easy for you to choose addresses that won't clash.

Unfortunately jails do not actually support restricting the use of IPv6
addresses right now.


More information about the freebsd-questions mailing list