Switching · 7 min read
Layer 2 vs Layer 3 Switches: Differences and When to Use Each
What is the difference between a Layer 2 and Layer 3 switch? Learn about VLANs, inter-VLAN routing, OSPF, where each switch fits in core, distribution and access layers.
When you design a business network, one of the first decisions is whether a switch should be Layer 2 or Layer 3. The answer affects performance, security and how your network grows.
What a Layer 2 switch does
A Layer 2 switch forwards Ethernet frames by MAC address. Managed Layer 2 switches add VLANs, QoS, link aggregation, loop protection and features such as 802.1X. They do not route between VLANs. Traffic from one VLAN to another must go to a router or a Layer 3 switch.
Typical Navijin examples: the GE6010-24P4S-L2 and the industrial GE2216-8P8S-L2.
What a Layer 3 switch adds
A Layer 3 switch can also route IP packets between subnets in hardware, at wire speed. It supports static routes and, on many models, dynamic routing such as RIP, OSPF and BGP, plus features like DHCP server or relay and ACLs between VLANs.
Navijin examples include the SG3801-24T4X, the NJS-9224X and the chassis-based DCS5503C.
Comparison table
| Layer 2 switch | Layer 3 switch | |
|---|---|---|
| Forwards by | MAC address | MAC and IP address |
| VLANs | Yes | Yes |
| Inter-VLAN routing | No (needs router) | Yes, in hardware |
| Dynamic routing | No | Static, and often OSPF/BGP |
| Typical layer | Access | Core and distribution, sometimes access |
| Cost | Lower | Higher |
Where each fits: the three-tier model
- Core: always Layer 3. It routes between buildings, the data center and the Internet edge.
- Distribution: Layer 3. It aggregates access switches and enforces policy between VLANs.
- Access: usually Layer 2 PoE switches connecting users, phones, cameras and APs. Use Layer 3 at the access layer in large campuses for smaller failure domains.
Smaller sites often collapse core and distribution into a single Layer 3 switch, the "collapsed core".
When a Layer 3 switch is the right choice
- You have several VLANs that need to talk to each other at high speed.
- The router is becoming a bottleneck for internal traffic.
- You need ACLs between departments, CCTV and guest networks.
- You connect multiple buildings or run dynamic routing.
Conclusion
Use Layer 2 managed switches at the edge and Layer 3 switches where traffic between networks meets. Not sure? Read about core switching or ask a Navijin engineer.
FAQ
Frequently asked questions
Can a Layer 3 switch replace a router?
For internal routing between VLANs and sites, often yes. For Internet edge functions such as NAT, VPN and firewalling, you still need a router, gateway or firewall.
Do I need a Layer 3 switch for VLANs?
No. Layer 2 switches support VLANs, but you need a Layer 3 device to route traffic between them.
Related
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