Contents
What causes a spanning tree topology change?
The network topology can happen in a network due to different reasons like a link failure, a Switch (Bridge) failure, or a port transitioning to forwarding state. The Root Switch (Bridge) bridge broadcasts the topology change information into the whole network.
What are topology changes?
A topology change occurs when a switch either moves a port into the Forwarding state or moves a port from the Forwarding or Learning states into the Blocking state. In other words, a port on an active switch comes up or goes down.
What is spanning tree topology?
The Spanning Tree Protocol (STP) is a network protocol that builds a loop-free logical topology for Ethernet networks. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them. RSTP was designed to be backwards-compatible with standard STP.
What happens when a switch receives a TCN?
When the switches receive this message they will reduce the aging time of the MAC address table from 300 seconds to 15 seconds (this is the forward delay timer). This message is called the TCN (Topology Change Notification). You can see that it received the topology change notification from SW1.
What triggers spanning tree?
Spanning tree in a nutshell Spanning tree recalculations are performed automatically when the network changes but cause a temporary network outage. Newer protocols, such as TRILL, prevent loops while keeping links that would be blocked by STP in service.
What is STP guard?
BPDU Guard is used to protect the Spanning Tree topology of a network by enforcing STP domain borders. It is recommended that BPDU Guard be applied to all access ports or client-facing ports that are not intended to be connected to a neighboring switch.
How many types of BPDU are there?
two kinds
There are two kinds of BPDUs for 802.1D Spanning Tree: Configuration BPDU, sent by root bridges to provide information to all switches. TCN (Topology Change Notification), sent by bridges towards the root bridge to notify changes in the topology, such as port up or port down.
What triggers spanning-tree?
When does topology change in a spanning tree protocol?
Topology Changes in Spanning Tree Protocol (STP) The network topology can happen in a network due to different reasons like a link failure, a Switch (Bridge) failure, or a port transitioning to forwarding state.
What are the topology changes in STP protocol?
Topology Changes in Spanning Tree Protocol (STP) 1 • The Switch (Bridge) notifies the topology change to Root Bridge More
When is a topology change generated by a switch?
A topology change (TC) is generated by a switch when one of the following condition occurs: – An interface that was previously in the spanning-tree FWD state goes DOWN – When a port transition to the FWD state The STP BPDU Filter feature ask your switch to stop sending/receiving BPDU.
When do bridges become aware of a topology change?
When the Root Switch (Root Bridge) is aware that there is a topology change in the network, it starts to send out its Configuration BPDUs with the topology change (TC) bit set. Configuration BPDUs are received by every Switch (Bridge) in the network and all bridges become aware of the network topology change.