I am using a bunch of Cisco 1721 routers for my T1 lines. We recently purchased Digi cell modems as a backup for the T1. On configuring vrrp to work on both devices I discovered that IOS 12.3(6c) does not support the "vrrp track" feature. After reviewing the Cisco Feature Navigator I could not see an IOS that will support the vrrp object tracking. Is that correct? The routers have T1 WIC's installed. If it does work what is the latest IOS that will work on this end of life product? Thanks..