#Packet tracer labs spanning tree how to#

UplinkFast provides fast convergence using uplink groups in the network access layer after a spanning tree topology change. BDPU filtering is on a per-switch basis after you enable BPDU filtering, it applies to all PortFast-enabled ports on the switch. When you enable PortFast on the switch, spanning tree places ports in the forwarding state immediately, instead of going through the listening, learning, and forwarding states.Д«y default, spanning tree sends BPDUs from all ports regardless of whether PortFast is enabled. Note When you enable BPDU guard on the switch, spanning tree applies BPDU guard to all PortFast-configured interfaces.Д«PDU filtering allows you to avoid transmitting BPDUs on PortFast-enabled ports that are connected to an end system. BPDU guard provides a secure response to invalid configurations because the administrator must manually put the interface back in service. If a PortFast-configured interface receives a BPDU, an invalid configuration exists. In a valid configuration, PortFast-configured interfaces do not receive BPDUs. When you enable BPDU guard on the switch, spanning tree shuts down PortFast-configured interfaces that receive BPDUs instead of putting them into the spanning tree blocking state. PortFast BPDU guard prevents loops by moving a nontrunking port into an errdisable state when a BPDU is received on that port. Because PortFast can be enabled on nontrunking ports connecting two switches, spanning tree loops can occur because BPDUs are still being transmitted and received on those ports. The most secure implementation of PortFast is to enable it only on ports that connect end stations to switches. To prevent loops from occurring in a network, the PortFast mode is supported only on nontrunking access ports because these ports typically do not transmit or receive BPDUs. Understanding How PortFast BPDU Guard Works When you enable PortFast on a switch or trunk port, the port is immediately transitioned to the spanning tree forwarding state. When the Forward Delay timer expires a second time, the port is transitioned to the forwarding or blocking state. When the Forward Delay timer expires, the port enters the learning state. When the switch powers up, or when a device is connected to a port, the port enters the spanning tree listening state. If you enable PortFast on a port that is connected to another Layer 2 device, such as a switch, you might create network loops. You can use PortFast on switch or trunk ports that are connected to a single workstation, switch, or server to allow those devices to connect to the network immediately, instead of waiting for the port to transition from the listening and learning states to the forwarding state.Д¬aution You can use PortFast to connect a single end station or a switch port to a switch port.

PortFast causes a switch or trunk port to enter the spanning tree forwarding state immediately, bypassing the listening and learning states.

Configuring Loop Guard Understanding How PortFast Works.

Understanding How PortFast BPDU Filtering Works.Understanding How PortFast BPDU Guard Works.Note For complete syntax and usage information for the commands that are used in this chapter, refer to the CatalystВ 4500В Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Command Reference.

#Packet tracer labs spanning tree how to#

This chapter describes how to configure the PortFast, BPDU guard, BPDU filter, UplinkFast, BackboneFast, and loop guard spanning tree enhancements on the Catalyst enterprise LAN switches. Understanding How PortFast BPDU Filtering Works

Configuring Spanning Tree PortFast, BPDU Guard, BPDU Filter, UplinkFast, BackboneFast, and Loop Guard Table Of ContentsД¬onfiguring Spanning Tree PortFast, BPDU Guard, BPDU Filter, UplinkFast, BackboneFast, and Loop Guard