Here are the most two disatvantages of STP:
1- Slow convergence:
The 15s listening state is to avoid temporary loops in the convergence process of the STP protocol, so that BPDUs have enough time to be transmitted throughout the network. During the listening state, the MAC address table will be prematurely affected by TC BPDUs, and the wrong MAC address information will be cleared, resulting in incorrect MAC address aging and idle MAC address aging. If you want to forward data frames at this time, it will cause a large number of unknowns. The DMAC unicast frames flood the network, which affects the network performance. Then we continue to sacrifice the 15s convergence time as the learning state. In this state, learn the MAC address table entries to reduce the number of unicast frames during the STP convergence period. Flooding behavior. The convergence of the STP protocol is completely dependent on the timer, and the convergence speed is slow. In order to solve the temporary loop and the flooding of unicast frames during the convergence period, it needs to wait 30s.
2- Low Link utilization:
STP is a single spanning tree protocol. In a network with multiple VLANs, all VLANs share one tree, resulting in
Link utilization low.
The access path is sub-optimal.
Inappropriate trunk configuration causes some vlan paths to fail.
therefore:
In order to solve the shortcomings of RSTP single tree, MSTP was developed
