Network licensing rules may be different in your country and region. Current license rules for products under Subscription allow Autodesk 2010 products to also license products up to three versions back. This means that under Subscription, you can license Autdoesk products for version releases of 2007, 2008, 2009, and 2010. This includes the versions of AutoCAD and its vertical products such as ACAD Electrical, MEP, etc. Please note that AutoCAD LT is not a network licensed product and is only offered as a stand-alone license activation.
Autodesk products prior to 2007 are considered retired and you will be unlikely to receive a license file for these products, especially if you have upgraded them to current versions. Additionally, you are not allowed to run more licenses than the total number of current licenses that you own. Therefore if you have 5 seats of AutoCAD 2009 that was upgraded via Subsription to 5 seats of AutoCAD 2010, you can run a total of 5 seats of AutoCAD 2009 and AutoCAD 2010 combined. You cannot, however, run 10 licenses total of these products.
Additionally, the current version of the Autodesk Network License Manager can be used for all Autodesk products starting with AutoCAD 2004. Releases of the product prior to AutoCAD 2004 use a different license manager system.
Please check with the reseller in your country if you have additional questions about your regional licensing.