CCNP-SWITCHING 300-115 Mohamed Samir YouTube channel Double CCIEs #27042(R/S&SP)

Part III Working with Redundant Links

Rapid Spanning Tree Protocol

SW2 SW1 FA0/1 FA0/1 FA0/11 FA0/2 FA0/2 FA0/11 FA0/1 FA0/1 FA0/2 FA0/2 SW4 SW3

Rapid Spanning Tree Protocol (802.1D) RSTP can be applied on instance or multiple Rapid PVST+ (RPVST+) and it can operate with MST as well Root port: best root path cost to the root Designated port: best root path cost to the Root Alternate port: less desirable than that of the root port Backup port: redundant (but less desirable) State the port Discarding:Incoming frames simply are dropped; no MAC addresses are learned Learning:Incoming frames are dropped, but MAC addresses are learned Forwarding: Incoming frames are forwarded according to MAC addresses that have been (and are being) learned.

BPDUs in RSTP The BPDU version also is set to 2 to distinguish RSTP BPDUs from 802.1D BPDUs BPDUs are sent out every switch port at hello time intervals … enhance max age time from 20 sec. to 6 sec. RSTP and STP are compatible and you can migrate without any disturbance

RSTP Convergence You can think of convergence as a two-stage process 1. One common root bridge must be “elected. 2. The state of every switch port Port Types Edge port: where only a single host connects “ portfast” if a BPDU ever is received on an edge port, the port immediately loses its edge port status. Root port: best cost to the root the other alternative root port Point-to-point port: A- Full duplex: STP will be quickly on this link Half duplex : shared media 802.1D traditional must ne run Synchronous process done to prevent the loop

Synchronization All port non-edge begin in Discarding state.

Topology Changes and RSTP Traditional STP TCN send by root bridge topology change (TC) messages propagate only when a nonedge port transitions to the Forwarding state BPDUs, with their TC bit set, are sent out all the nonedge designated ports.(two hello interval) all MAC addresses associated with the nonedge designated ports are flushed

RSTP Configuration By default, a switch operates in Per-VLAN Spanning Tree Plus (PVST+) mode using traditional 802.1D STP RSTP cannot be used until a different spanning-tree mode (MST or RPVST+) To configure a port as an RSTP edge port Switch(config-if)# spanning-tree portfast It should automatic detect point to point but to force you can use Switch(config-if)# spanning-tree link-type point-to-point Switch(config)# spanning-tree mode rapid-pvst Be careful STP process that is currently running must be restarted.

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