One access switch configured with two VLANs

A single access switch can support multiple VLANs by assigning different ports to each VLAN, but devices in separate VLANs require inter-VLAN routing to communicate.VLAN Basics on a Single SwitchVLANs (Virtual Local Area Networks) allow you to logically segment a physical switch into separate broadcast domains, improving security and reducing unnecessary traffic . On a single switch, each port can be assigned to a specific VLAN. For example, you could configure:Ports 1–10 for VLAN 10Ports 11–20 for VLAN 20 Devices connected to ports in VLAN 10 can communicate freely with each other, but they are isolated from devices in VLAN 20 unless routing is configured .Configuring Access PortsEach switch port is configured as an access port for a specific VLAN. On Cisco switches, the commands typically look like this:CodeCopySwitch(config)# interface FastEthernet0/1Switch(config-if)# switchport mode accessSwitch(config-if)# switchport access vlan 10Switch(config-if)# exitSwitch(config)# interface FastEthernet0/2Switch(config-if)# switchport mode accessSwitch(config-if)# switchport access vlan 20 This ensures that traffic from each port is tagged with the correct VLAN internally, even though access ports do not tag frames externally .Inter-VLAN CommunicationDevices in different VLANs cannot communicate directly at Layer 2. To enable communication between VLAN 10 and VLAN 20, you need inter-VLAN routing, which can be done using:A router with subinterfaces for each VLANA Layer 3 switch with Switched Virtual Interfaces (SVIs) for each VLAN For example, on a Layer 3 switch:CodeCopySwitch(config)# interface vlan 10Switch(config-if)# ip address 192.168.10.1 255.255.255.0Switch(config-if)# no shutdownSwitch(config)# interface vlan 20Switch(config-if)# ip address 192.168.20.1 255.255.255.0Switch(config-if)# no shutdown Devices in VLAN 10 would use 192.168.10.1 as their default gateway, and devices in VLAN 20 would use 192.168.20.1. This allows routing between VLANs while maintaining logical separation .Important ConsiderationsIP Subnets: Each VLAN should have a unique IP subnet to avoid conflicts and ensure proper routing .VLAN Mismatch: When connecting multiple switches, ensure VLANs match on trunk or access ports to prevent communication issues .Security and Performance: VLANs improve security by isolating traffic and reduce broadcast traffic, enhancing network performance . By properly configuring access ports and inter-VLAN routing, a single switch can effectively manage multiple VLANs while controlling communication between them.