CCNA Explorer 3 STP

STP

Redundant Layer 2 Topologies

Redundancy

Simple network VLAN mangement

Starting point

Path Failure - Access to Distribution

Path Failure - Distribution to Core

Switch Failure - Distribution layer

Switch Failure - Core layer

Issues with Redundancy Layer 2 Loops Broadcast loops Real-world Redundancy Issues Non-Redundant network topology Loops from 2 connections in the same switch Loops from connections to a second switch Loops int the cubicles Introduction to STP The Spanning Tree Algorithm STP Topology STP Redundancy STP Port names Root ports - Switch ports closest to the root bridge. Designated ports - All non-root ports that are still permitted to forward traffic on the network. Non-designated ports - All ports configured to be in a blocking state to prevent loops. Root Bridge BID fields Port cost Configuring port costs Path Cost Verify port and path costs STP BPDU BPDU Fields Version - The version field indicates the version of the protocol, This field contains the value zero. Message type - The message type field indicated the type of message, this field contains the value zero. Flags - The flags field includes one of the following: Topology change(TC) bit, which signals a topology change in the event a path to the root bridge has been disrupted. Topology change acknowledgment(TCA) bit, which is set to acknowledge receipt of a configuration messege with the TC bit set. Root ID - The Root ID field indicates the root bridge by listing its 2-byte prority followed by its 6-byte MAC address ID. Bridge ID - The Bridge ID field indicates the priority and MAC address ID of the bridge sending the message Port ID - The Port ID field indicates the port number from which the configuration message was sent. Forward Delay - The Forward delay field indicates the length of time that bridges should wait before transitioning to a new state after topology change. BPDU Fields BPDU Process Step 1 BPDU Process Step 2 BPDU Process Step 3 BPDU Process Step 4 BPDU Process Step 5 BPDU Process Step 6 BPDU Process Step 7 BPDU Process Step 8 BPDU Process Step 9 Bridge ID BID Fields Priority-based desicions MAC Address-based desicions Configure STP Verify STP Port Roles Root Port The root port exists on non-root bridges and is the switch port with the best path to the root bridge. Designated Port The designated port exists on root and non-root bridges. For root bridges, all switch ports are designated ports. Only one designated port is allowed per segment. Designated ports are capable of populating the MAC table. Non-designated Port The non-designated port is a switch port that is blocked, so it is not forwarding data frames and not populating the MAC address table with source addresses. Disabled Port The disabled port is a switch port that is administratively shut down. STP Port Roles STP Port Roles Configure port priority Verify Port Roles and Priority STP Port States and BPDU Timers STP Port States BPDU Timers BPDU Roles and Timers Configure network diameter Cisco Portfast technology Configure portfast Verify portfast STP Convergence STP Convergence STP Convergence Step 1. Electing A Root Bridge Electing a root bridge Step 2. Elect Root Ports Elect a root port step 1 Elect a root port step 2 Elect a root port step 3 Elect a root port step 4 Step 3. Electing Desgnated Ports and Non-Designated Ports Elect port step 1 Elect port step 2 Elect port step 3 Elect port step 4 Elect port step 5 Elect port step 6 Elect port step 7 STP Topology Change STP Topology Change Topology change notification(TCN) messages are flooded out the root port, until it reaches the root bridge. STP Broadcast notification The Root Bridge broadcasts Topology change messages PVST+, RSTP and Rapid-PVST+ Cisco and STP Variants STP Variants PVST+ PVST+ PVST+ Bridge ID PVST+ Bridge ID example Default PVST+ configuration Configure PVST+ Configure PVST+ Configure PVST+ Priority Verify PVST+ RSTP RSTP Characteristics of RSTP RSTP BPDU Edge Ports Edge Ports Link Types Link Types Point-to-point Link Type - Links attaches to switch ports that are operating in full-duplex mode Shared Link Type - This link is attached to a port that is operating in half-duplex mode RSTP Port States and Port Roles RSTP Port States RSTP Port States RSTP Port States RSTP Port Roles Configure Rapid-PVST+ Rapid-PVST+ Topology Rapid-PVST+ Example configuration Rapid-PVST+ verification Design STP for Trouble Avoidance Know where the root is Manual Pruning Layer 3 Switching Layer 3 Switching Troubleshoot STP Operation Troubleshoot a failure PortFast configuration error Network diameter issues Chapter Summary Chapter summary