Reef Basics - Configuring VLANs on Cisco Switches and Routing Between them

August 27, 2025

How to Configure VLANs and Routing for Cisco 3850 (and Most Cisco Switches): Reef Telecom Guide

What Are VLANs?

VLANs (Virtual Local Area Networks) logically group devices to create separate networks—improving performance, security, and management.
Inter-VLAN routing allows devices in different VLANs to communicate via the switch’s routing capability (Layer 3).

Step 1: Create VLANs

Step 2: Assign IP Subnets to Each VLAN (SVI Creation)

Step 3: Assign Ports to VLANs

interface range GigabitEthernet1/0/1-10
switchport mode access
switchport access vlan 10
spanning-tree portfast
interface range GigabitEthernet1/0/11-20
switchport mode access
switchport access vlan 20
spanning-tree portfast

Step 4: Enable IP Routing on the Switch

How It Works

Devices in VLAN 10 get IPs in 192.168.10.0/24.
Devices in VLAN 20 get IPs in 192.168.20.0/24.
The switch, with interfaces vlan 10 and vlan 20 configured and ip routing enabled, routes traffic between VLANs automatically.
Add a default router (gateway) for external traffic if needed.

Copy-Paste Config Example:

vlan 10
name OFFICE_DEVICES
vlan 20
name GUEST_WIFI

interface vlan 10
ip address 192.168.10.1 255.255.255.0
no shutdown

interface vlan 20
ip address 192.168.20.1 255.255.255.0
no shutdown

interface range GigabitEthernet1/0/1-10
switchport mode access
switchport access vlan 10
spanning-tree portfast

interface range GigabitEthernet1/0/11-20
switchport mode access
switchport access vlan 20
spanning-tree portfast

ip routing

FAQs & Pro Tips

Can I use this on a 2960, 9300, or 4500 series?
Yes! While only Layer 3 switches support inter-VLAN routing, creating VLANs and assigning ports applies to almost all Cisco switches.
How do hosts get addresses?
Use a DHCP server with scopes for each VLAN, or configure the switch as a DHCP helper.
Can I add more VLANs?
Yes! Repeat the above process with new VLAN IDs and subnet ranges.
How do I block or restrict VLAN traffic?
Apply ACLs (Access Control Lists) on VLAN interfaces (“SVIs”).

Show/Verification Commands

For secure, scalable VLAN deployments, trust Reef Telecom—your Cisco networking experts!