We have an old Cisco 6509 with 2 x Sup-720w/MSFC3 running 12.2(18)SXD6. IOS version is pretty old, and Cisco's software download section doesn't even have it in the list anymore.
We would like to upgrade IOS to the newest/latest, but we're not sure what the minimum IOS version that we need to put, in order to get to the latest IOS version. Can someone please help?
Thank you,