Upgrading from Fedora 9 directly to Fedora 11 using yum is not possible, you must upgrade to Fedora 10 first, then upgrade to Fedora 11. See http://fedoraproject.org/wiki/YumUpgradeFaq for more information. You can also use preupgrade to upgrade directly to Fedora 11 using anaconda, minimizing the system downtime by downloading the packages in advance.
I read this in the Fedora 11
I read this in the Fedora 11 release notes
Upgrading from Fedora 9 directly to Fedora 11 using yum is not possible, you must upgrade to Fedora 10 first, then upgrade to Fedora 11. See http://fedoraproject.org/wiki/YumUpgradeFaq for more information. You can also use preupgrade to upgrade directly to Fedora 11 using anaconda, minimizing the system downtime by downloading the packages in advance.
at:
http://docs.fedoraproject.org/release-notes/f11preview/en-US/ar01s02s02....
So the devil is in the details. How this works for a typical LTSP setup is non-trivial to me.