Following this tutorial I get this error on raring:
juju bootstrap
2013-01-16 02:19:07,091 INFO Bootstrapping environment 'sample' (origin: ppa type: local)...
2013-01-16 02:19:07,092 INFO Checking for required packages...
2013-01-16 02:19:07,512 INFO Starting networking...
2013-01-16 02:19:07,540 ERROR [Errno 99] Cannot assign requested address
For future reference, this bug on launchpad.