Most newer Cisco switches use RSTP by default. RSTP prevents frame looping out of the box and no additional configuration is necessary. To check whether a switch runs RSTP, the show spanning-tree command is used:
SW1#show spanning-tree
VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 32769
Address 0004.9A47.1039
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0004.9A47.1039
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/3 Desg FWD 19 128.3 P2p
Fa0/2 Desg FWD 19 128.2 P2p
If RSTP is not being used, the following command will enable it:
SW1(config)#spanning-tree mode rapid-pvst
Most other configuration options (electing root switch, selecting root and designated ports) are similar to the ones used in STP.