Hello Sathish
Strictly speaking, Uplinkfast will employ the root port delay timer whenever the original root port that failed comes back up. That delay timer according to Cisco is 50 seconds and is not configurable.
However, there could be several reasons for the behavior you are seeing.
- UplinkFast is not part of the original STP design, it is a Cisco enhancement designed to improve convergence, so its implementation may vary from platform to platform.
- The behavior described in the lesson is for the original 802.1D standard. Using a different type of STP may affect the behavior of uplinkfast.
- For example, if the default STP version on your device is RSTP, then the Uplinkfast configuration will have little effect because RSTP inherently reconverges quickly and ignores any uplinkfast configurations.
When you enable UplinkFast on a switch, it increases the bridge priority to 49152 to ensure that the switch won’t become the root bridge, since UplinkFast is designed for non-root switches. The interface cost is increased to 3100 to prevent the switch from becoming a designated switch on any of the connected segments.
The convergence time for selecting a root bridge can vary based on several factors, such as the number of switches in your network, the speed of your links, the current load on your network, and the specific STP enhancements you have enabled (like RSTP, UplinkFast, or BackboneFast). It’s normal to see some variability in convergence time during your lab tests. If you want to speed up the convergence time, you can consider enabling RSTP or tuning your STP timers.
I hope this has been helpful!
Laz