I think you have to upgrade to 10.x first. I'd suggest 10.2.0 as that's where 11.x was branched from 10.x.
The release notes state that you can't upgrade from any 9.x version to 11.1:
http://support.f5.com/kb/en-us/products/big-ip_ltm/releasenotes/product/relnote-ltm-11-1-0.htmlrns_upgrade
Upgrading from versions earlier than 10.x
You cannot roll forward a configuration directly to this version from BIG-IP version 4.x, or from BIG-IP versions 9.0.x through 9.6.x.
You must be running version 10.x software. For details about upgrading to those versions, see the release notes for the associated release.
Aaron
Nimbostratus
