switching

name	switching
description	Network switching fundamentals
license	MIT
compatibility	opencode
metadata	{"audience":"network-engineers","category":"networking"}

What I do

• Configure and manage network switches
• Implement VLANs and trunking
• Configure spanning tree protocols
• Set up switch stacking and stacking
• Manage VLAN routing (SVI)
• Implement port security
• Configure switch monitoring

When to use me

Use me when:

• Designing local area networks
• Configuring access/aggregation switches
• Implementing network segmentation
• Troubleshooting connectivity issues
• Setting up switch infrastructure

Key Concepts

Layer 2 Switching

Switches operate at Layer 2, forwarding based on MAC addresses:

┌─────────────────────────────────────┐
│         Switch Forwarding           │
├─────────────────────────────────────┤
│ MAC Address Table (CAM Table)       │
│ Port 1: aa:bb:cc:dd:ee:ff          │
│ Port 2: 11:22:33:44:55:66          │
│ Port 3: aa:bb:cc:dd:ee:11          │
└─────────────────────────────────────┘

Frames forwarded based on:
- Destination MAC known → Forward to port
- Unknown → Flood to all ports
- Broadcast → Flood to all ports

VLAN Configuration

! Create VLANs
vlan 10
  name Data
vlan 20
  name Voice
vlan 99
  name Management

! Assign ports to VLANs
interface GigabitEthernet0/1
  switchport mode access
  switchport access vlan 10
  spanning-tree portfast

! Trunk port
interface GigabitEthernet0/24
  switchport trunk encapsulation dot1q
  switchport mode trunk
  switchport trunk allowed vlan 10,20,99

Spanning Tree Protocol

• STP: 802.1D, 50-second convergence
• RSTP: 802.1w, rapid convergence
• MSTP: 802.1s, multiple spanning trees
• PVST+: Per-VLAN STP (Cisco)

Switch Features

• Port Security: Limit MAC addresses
• DHCP Snooping: Prevent rogue servers
• ARP Inspection: Prevent ARP spoofing
• Storm Control: Broadcast suppression
• QoS: Traffic prioritization