Spanning tree is the L2 control plane protocol we have to ensure a loop-free network. It does so by blocking redundant links. Topology Here, SW1 is the root switch with a priority of 4096. SW2 has been configured for root secondary. SW3 is default. Ultimately these configurations result in the above converged STP topology. Initial configurations SW1 SW1#sh run | sec span spanning-tree mode pvst spanning-tree loopguard default spanning-tree extend system-id spanning-tree vlan 1-4094 priority 4096 SW1# SW2 SW2#sh run | sec span spanning-tree mode pvst spanning-tree loopguard default spanning-tree extend system-id spanning-tree vlan 1-4094 priority 28672 SW2# SW3 SW3#sh run | sec span spanning-tree mode pvst spanning-tree loopguard default spanning-tree extend system-id SW3# Loop Guard Loop guard is an STP enhancement.