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Why has Spanning Tree placed a port in blocking state?
The Switch Ports will go into a blocking state at the time of election process, when a switch receives a BPDU on a port that indicates a better path to the Root Switch (Root Bridge), and if a port is not a Root Port or a Designated Port.
What state is the root port on a switch when in STP operation?
A switch port receives superior BPDUs from another switch and identifies that switch as the root bridge. The port with the lowest root path is selected as the root port, if possible.
How do I know if a port is spanning-tree blocking?
Use the show spanning-tree blockedports command to display the ports that are blocked by STP. Use the show mac address-table dynamic vlan command to determine if learning or aging occurs at each node.
How long does it take to bring up a port from blocking to forwarding?
When a port is not a designated or root port it will be in blocking mode. This means it takes 30 seconds in total to move from listening to forwarding…that’s not really fast right?
What do I need to know about STP troubleshooting?
Verify the type of spanning tree configured on your device, and that STP is turned on. If all the switches are on the same mode, we can move on with troubleshooting. If they are on different modes, we need to correct this, and then test. • stp — Spanning Tree Protocol (STP) is enabled.
What happens when STP is disabled on a Cisco switch?
• BPDU Flood — When enabled, the BPDU Flood feature floods the BPDU traffic arriving on this port when STP is disabled on this port. Find the root bridge, then learn the designated ports on each subsequent switch. Cisco switches run PVST by default so you will have to work through each vlan.
When does a port go into a blocking state?
Blocking State The Switch Ports will go into a blocking state at the time of election process, when a switch receives a BPDU on a port that indicates a better path to the Root Switch (Root Bridge), and if a port is not a Root Port or a Designated Port.
What does number of topology changes mean in STP?
To verify, run the command: When the ‘Number of topology changes’ increases, it typically means that the physical state of a port on the switch is changed. If there is an increase in topology changes, continue with verifying non-edge interface state changes. If there is not an increase then move one to analyzing traffic for unusually heavy traffic.