In your previous mail you wrote: There are a number of advantages of non-/64 for p2p. For example, you can have an easy address allocation scheme like ...:<router number>:<index>:<host id>" which does not require any bookkeeping. That's not possible with /64 addresses. => I strongly disagree. IMHO your claim is based on the false assumption that EUI-64 is mandatory. The standard also requires EUI-64 addresses which is clearly not => NO, EUI-64 is not mandatory. Only the modified EUI-64 *format* is mandatory: you can put what you want in 63 bits if one bit is set to zero. desirable for a number of application. For example, it would be very silly to require a change all your peering sessions just because you change your NIC. => I agree but as EUI-64 is not mandatory I have no problem too... So it is obvious that the requirement for EUI-64 cannot be taken too seriously, and consequently the requirement for a /64 seems not convincing either. => of course it cannot be taken too seriously because it doesn't exist (:-). But the requirement for a /64 is a real one. Regards Francis.Dupont@enst-bretagne.fr