How to Prevent Network Loops With Spanning Tree (RSTP)

Step by step

1. Enable RSTP everywhere

   Use the same mode on every switch.

   spanning-tree mode rstp
   

2. Make the core switch the root

   Set the lowest priority on the core so the topology is predictable.

   spanning-tree priority 4096
   

3. Mark edge ports

   Ports to PCs, phones and cameras should start forwarding immediately.

   interface range gigabitEthernet 0/1-24
    spanning-tree portfast
   

4. Enable BPDU guard

   If someone plugs a switch into a user port, the port shuts down instead of creating a loop.

   interface range gigabitEthernet 0/1-24
    spanning-tree bpduguard enable
   

5. Verify

   Check the root bridge and port roles.

   show spanning-tree
   

Commands are generic, industry-standard examples. Exact syntax and menu names vary by model and firmware; check your device's manual on the Documentation page.