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CCNA 2.6.a: STP mode (PVST+ and RPVST+)

Overview: Per-VLAN Spanning-Tree plus and Rapid PVST+ are enhancements to 802.1D STP

Study Notes:

  • 802.1D Spanning Tree Protocol (STP) has a drawback of slow convergence
  • Cisco Catalyst switches support three types of STPs, which are PVST+, rapid-PVST+ and MST.

Per-VLAN Spanning-Tree plus (PVST+)

  • PVST+ is based on IEEE802.1D standard and includes Cisco proprietary extensions such as BackboneFast, UplinkFast, and PortFast

Rapid Per-VLAN Spanning-Tree plus (PVST+)

  • Rapid-PVST+ is based on IEEE 802.1w standard and has a faster convergence than 802.1D
    • Uses Bridge Protocol Data Unit (BPDU) version 2 which is backward compatible with the 802.1D STP, which uses BPDU version 0
    • All the switches generate BPDUs and send out on all the ports every 2 seconds, whereas in 802.1D STP only the root bridge sends the configuration BPDUs
    • Port Roles—Root port, Designated port, Alternate port and Backup port
    • Port States—Disabled, Blocking, Listening, Learning, and Forwarding
    • Port Types—Edge Port (PortFast), Point-to-Point and Shared portRSTP (IEEE 802.1w) natively includes most of the Cisco proprietary enhancements to the 802.1D Spanning Tree, such as BackboneFast and UplinkFast. Rapid-PVST+ has these unique features:
  • Rapid-PVST uses RSTP to provide faster convergence. When any RSTP port receives legacy 802.1D BPDU, it falls back to legacy STP and the inherent fast convergence benefits of 802.1w are lost when it interacts with legacy bridges.
  • The configuration of the features such as PortFast, BPDUguard, BPDUfilter, root guard, and loopguard are applicable in rapid-PVST+
  • Migrating from PVST+ to Rapid-PVST+ will most likely cause network disruptions as Spanning-Tree reconverges

 

PacketTracer Lab: CCNA-2.6.a-How-to-configure-STP-mode-PVST-and-RPVST.pkt

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Links: https://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/72836-rapidpvst-mig-config.html


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