IPv6 ULA Address Assignment problem
 

I use network congiuration and I assign this address:

IPadderss = fd66:9c7b:681b:0001:0a00:27ff:feB3:d3c1
subnet mask = /64
default gateway = [unspecified]
primary dns = [unspecified]
secondary dns = [unspecified]

when i click ACTIVATE i get this error:

ipcalc: bad netmask: /64
ipcalc: bad netmask: /64
ipcalc: bad netmask: /64
arping: unknown host fd66:9c7b:681b:0001:0a00:27ff:feB3:d3c1
Error, some other host already uses address fd66:9c7b:681b:0001:0a00:27feB3:d3c1.

I am using Fedora 11 with latest updates!