🔧 Technical Overview
| Feature/Aspect | Layer 2 Switch | Layer 3 Switch |
|---|---|---|
| OSI Layer | Layer 2 (Data Link) | Layer 3 (Network) |
| Main Function | Switching (MAC-based forwarding) | Routing + Switching (IP-based forwarding) |
| Addressing | Uses MAC addresses | Uses IP addresses |
| Switching Method | Ethernet frame forwarding | IP packet routing and Ethernet switching |
| Table Used | MAC Address Table | Routing Table + MAC Table |
| Inter-VLAN Routing | ❌ Not natively supported (requires external router) | ✅ Supported internally |
| Routing Protocols | ❌ None | ✅ Supports static and dynamic protocols (OSPF, BGP, RIP) |
| Packet Forwarding | Hardware-based (ASIC) | Hardware-based with routing intelligence |
| Broadcast Domains | Single (unless VLANs are configured) | Can route between VLANs (multiple domains) |
📈 Performance and Scalability
| Feature | Layer 2 Switch | Layer 3 Switch |
|---|---|---|
| Latency | Lower (less processing) | Slightly higher (routing logic) |
| Scalability | Limited (dependent on VLANs, STP) | More scalable (can segment networks logically) |
| Congestion Handling | VLANs, STP, and QoS | VLANs, STP, Routing, ACLs, QoS |
| Network Segmentation | Requires VLAN and router | Native VLAN routing support |
| Resilience | STP, RSTP | HSRP, VRRP, ECMP (load-balanced paths) |
| Security | Port Security, 802.1X | ACLs, Route filtering, VRFs |
🧰 Use Cases
| Scenario | Best Fit |
|---|---|
| Small Office or LAN with few VLANs | L2 Switch |
| Access layer for desktops, phones, printers | L2 Switch |
| Campus Core/Distribution layer | L3 Switch |
| Data center with multiple VLANs/subnets | L3 Switch |
| Inter-VLAN Routing without external routers | L3 Switch |
| Routing between IP networks | L3 Switch |
| Security segmentation with ACLs | L3 Switch |
| Static/Dynamic Routing | L3 Switch |
🛡️ Security Features Comparison
| Security Capability | L2 Switch | L3 Switch |
|---|---|---|
| MAC Filtering | ✅ | ✅ |
| VLAN Segmentation | ✅ | ✅ |
| ACLs (IP-based) | ❌ | ✅ |
| DHCP Snooping, Dynamic ARP Inspection | ✅ | ✅ |
| Routing-based Access Control | ❌ | ✅ |
| Port Isolation | ✅ | ✅ |
🧠 Smarts & Intelligence
| Intelligence Type | L2 Switch | L3 Switch |
|---|---|---|
| Learning | MAC address learning | MAC + Route learning |
| Decision Making | Forward frames based on MAC | Forward packets based on IP |
| Path Selection | None (STP only) | Dynamic via routing protocols |
| Redundancy Protocols | STP, RSTP | STP + HSRP, VRRP, ECMP |
💰 Cost & Complexity
| Metric | Layer 2 Switch | Layer 3 Switch |
|---|---|---|
| Cost | Cheaper | More expensive |
| Configuration Complexity | Simpler | More complex (routing, ACLs) |
| Management Overhead | Lower | Higher |
| Power Consumption | Lower | Higher (more logic circuitry) |
🏁 Summary: When to Use What
| Use Case | Recommended |
|---|---|
| Pure L2 switching for access layer | L2 Switch |
| Inter-VLAN Routing in campus core | L3 Switch |
| High-speed data center routing/switching | L3 Switch |
| Minimal complexity, flat network | L2 Switch |
| Need for routing protocols & ACLs | L3 Switch |
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