Course Content
Packet Forwarding
0/2
Network Device Communication
Forwarding Architectures
Spanning Tree
An overview of how switches become aware of other switches and prevent loops.
0/2
Spanning Tree Protocol Fundamentals
Rapid Spanning Tree Protocol
Advanced Spanning Tree Tuning
0/2
Spanning Tree Topology Tuning
Additional Spanning Tree Protection Mechanisms
Multiple Spanning Tree Protocol (MST)
0/1
Multiple Spanning Tree Protocol
VLAN Trunks and EtherChannel Bundles
0/3
VLAN Trunking Protocol (VTP)
Dynamic Trunking Protocol (DTP)
EtherChannel Bundle
IP Routing Essentails
0/4
Routing Protocol Overview
Path Selection
Static Routing
Virtual routing and forwarding (VRF)
EIGRP
0/4
EIGRP Fundamentals
EIGRP Path Metric Calculation
EIGRP Failure Detection and Timers
EIGRP Route Summarization
OSPF
0/4
OSPF Fundamentals
OSPF Configuration
OSPF Default Route Advertisement
Common OSPF Optimizations
Advanced OSPF
The (OSPF) protocol scales well with proper network planning. IP addressing schemes, area segmentation, address summarization, and hardware capabilities for each area should considered when designing a network.
0/6
OSPF Areas
OSPF Link-State Announcements
Discontiguous Networks
OSPF Path Selection
OSPF Routes Summarization
OSPF Route Filtering
OSPFv3
0/3
OSPFv3 Fundamentals
OSPFv3 Configurations
IPv4 Support in OSPFv3
BGP
0/4
BGP Fundamentals
Basic BGP Configuration
BGP Route Summarization
Multiprotocol BGP for IPv6
Advanced BGP
0/6
BGP Multihoming
BGP Conditional Matching
BGP Route Maps
BGP Route Filtering and Manipulation
BGP Communities
BGP Path Selection
Multicast
0/5
Multicast Fundamentals
Multicast Addressing
Internet Group Management Protocol
Protocol Independent Multicast
Rendezvous Points
QoS
0/5
The Need for QoS
QoS Models
Classification and Marking
Policing and Shaping
Congestion Management and Avoidance
IP Services
0/3
Time Synchronization
First Hop Redundancy Protocol
Network Address Translation
Overlay Tunnels
0/4
Generic Routing Encapsulation (GRE) Tunnels
IPsec Fundamentals
Cisco Location/ID Separation Protocol (LISP)
Virtual Extensible Local Area Network (VXLAN)
Wireless Signals & Modulation
0/2
Understanding Basic Wireless Theory
Carrying Data over a Wireless Signal
Wireless Infrastructure
0/3
WLAN Topologies
Leveraging Antennas for Wireless Coverage
Pairing Lightweight APs and WLCs
Understanding Wireless Roam and Location Services
0/3
Roaming Overview
Roaming Between Centralized Controllers
Locating Devices in a Wireless Network
Authenticating Wireless Clients
0/4
Open Authentication
Authenticating with Pre-Shared Key (PSK)
Authenticating with EAP
Authenticating with WebAuth
Troubleshooting Wireless Connectivity
0/2
Troubleshooting Client Connectivity from WLC
Troubleshooting Connectivity Problems at the AP
Enterprise Network Architecture
0/2
Hierarchical LAN Design Model
Enterprise Network Architecture Options
Fabric Technologies
0/2
Software-Defined Access (SD-Access)
Software Defined WAN (SD-WAN)
Network Assurance
0/6
Network Diagnostic Tools
Debugging
NetFlow and Flexible NetFlow
Switched Port Analyzer (SPAN) Technologies
IP SLA
DNA Center Assurance
Secure Network Access Control
0/3
Network Security Design for Threat Defense
Network Access Control (NAC)
Next-Generation Endpoint Security
Network Device Access Control and Infrastructure Security
0/5
Access Control Lists (ACLs)
Terminal Lines and Password Protection
Authentication, Authorization, and Accounting (AAA)
Zone-Based Firewall (ZBFW)
Control Plane Policing (CoPP)
Virtualization
0/2
Server Virtualization
Network Functions Virtualization
Foundational Network Programmability Concepts
0/6
CLI
Application Programming Interface (API)
Data Models and Supporting Protocols
DevNet
GitHub
Basic Python Components and Scripts
Introduction to Automation Tools  
To provide a high-level overview of some of the most common configuration management and automation tools that are available.
0/3
Embedded Event Manager (EEM)
Agent-Based Automation Tools
Agentless Automation Tools
ENCOR Course
About Lesson

Spanning Tree Topology Tuning

some of the options for modifying the root bridge location or moving blocking ports to designated ports.

  • In a properly designed network a switch is deliberately selected to become the root bridge and the designated and alternate ports are modified.
  • Network design considerations factor in hardware platform, resiliency, and network topology.

Root Bridge Placement

To ensure root bridge placement set the system priority on:

  • The root bridge to the lowest value
  • The secondary root bridge to a value slightly higher than that of the root bridge
  • All other switches to a value higher than the secondary root bridge
Command Description
spanning-tree vlan vlan-id priority priority The priority is a value between 0 and 61,440, in increments of 4,096.
spanning-tree vlan vlan-id root {primary | secondary} [diameter diameter] The primary keyword sets the priority to 24,576, and the secondary sets the priorityto 28,672. The optional diameter commandmakes it possible to tune STP convergenceand modifies the timers.

Configuring the Root Bridge

  • The initial priority for VLAN 1 on SW1 verified, 32,769.
  • SW1 is configured to be the primary root for VLAN 1
  • The priority is verified again to ensure the change took place.

Configuring the Backup Root Bridge

  • The initial priority for VLAN 1 on SW2 is verified, 32,769.
  • SW2 configured to be the secondary root
  • The priority is verified again to ensure the change took place.

Modifying STP Root Port & Blocked Switch Port Locations

 

Calculating total path cost to the root bridge:

  • SW1 sends a BPDU to SW3 with the path cost of 0.
  • SW3 receives the BPDU and adds its root port cost (4) to cost from the BPDU (0), resulting in the cost of 4.
  • SW3 sends a BPDU to SW5 with the path cost of 4.
  • SW5 receives the BPDU and adds its root port cost (4) to the cost from the BPDU (4), resulting in the cost of 8 for SW5 to reach the root bridge.

Verifying the Total Path Cost

The example highlights the total path cost to the root bridge from SW3 and SW5. Note: There is not a total path cost in SW1’s output

Modifying STP Port Cost

  • The spanning tree [vlan vlan-id] cost cost command can be used to modify the STP forwarding path.
  • Using the spanning tree command will modify the cost for all VLANs unless the optional vlan keyword is used.

Modifying STP Port Priority

STP port priority influences which port becomes the alternate port when multiple links are used between switches. Use the command spanning -tree [vlan vlan-id] port-priority priority to change the STP port priority on a switch’s interface.

 

 

Other useful information:

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