The Lazy Networker

Spanning Tree Protocol (STP) helps prevent Layer 2 loops, but misconfigurations and failures can still cause network outages. Here’s how to troubleshoot common STP issues effectively. 🔍 1️⃣ Issue: Network Loop / Broadcast Storm 🚨 Symptoms:✅ High CPU utilization on switches.✅ MAC address table fluctuates rapidly.✅ End devices lose connectivity…

To prevent switching loops, unauthorized topology changes, and misconfigurations, Cisco offers several Spanning Tree Protocol (STP) protection mechanisms: 1️⃣ BPDU Guard (Prevents Unauthorized Switches) ✅ Purpose: Disables a port if it receives a BPDU.✅ Use Case: Prevents unauthorized switches from connecting to PortFast-enabled ports.🚨 Applies to: Access ports (where only…

Cisco introduced these STP enhancements to speed up convergence and improve network reliability. Let’s break them down! 1️⃣ PortFast (Edge Port) ✅ Purpose: Bypasses STP states (Listening & Learning) to immediately forward traffic.✅ Use Case: For end-user devices (PCs, printers, servers) to reduce boot time delays.🚨 Warning: DO NOT enable…

Cisco switches support Per-VLAN Spanning Tree (PVST) and Rapid Per-VLAN Spanning Tree (Rapid PVST) to prevent Layer 2 loops. Let’s compare them! 1️⃣ What is PVST? (Per-VLAN Spanning Tree) ✅ Cisco proprietary version of STP.✅ Runs one STP instance per VLAN.✅ Based on IEEE 802.1D (classic STP) → Slow (50…

Scenario: Network Loop and High CPU Usage Company ABC has a redundant Layer 2 network using Rapid Spanning Tree Protocol (RSTP). Users report network slowdowns, high latency, and intermittent connectivity. The network administrator notices that CPU usage on the core switch is spiking to 90%. Symptoms Observed: ✅ High CPU…

1️⃣ The Problem: Why Do We Need STP? In a redundant Layer 2 network, multiple paths exist between switches to improve reliability. However, this can cause switching loops, leading to: 🚨 Broadcast Storms – Frames endlessly circulate, consuming bandwidth.🚨 MAC Table Instability – Switches receive frames on multiple interfaces, confusing…

STP operates by transitioning ports through different states to avoid loops while still allowing network connectivity. Each port in STP can be in one of the following states: 1️⃣ Disabled State 🔴 Not part of STP operation 🔹 Command to Disable a Port: Switch(config)# interface GigabitEthernet0/1Switch(config-if)# shutdown 2️⃣ Blocking State…

Spanning Tree Protocol (STP) is a Layer 2 protocol designed to prevent loops in a switched network. It ensures there is only one active path between switches, preventing broadcast storms, MAC table instability, and duplicate frames. Why is STP Needed? In a redundant network, loops can form because switches forward…

Scenario: A network administrator configures EtherChannel between two Cisco switches using LACP, but the link is not forming, and some VLANs are not passing traffic. Network Setup: Step 1: Verify EtherChannel Status Check the current EtherChannel summary on SW1 SW1# show etherchannel summary Output: Group Port-channel Protocol Ports—— ———— ——–…