Add VLAN to core switch

To add VLANs on a Cisco core switch, you create the VLAN in global configuration mode, optionally name it, and assign switch ports to the VLAN or configure trunk ports for inter-switch communication.Step 1: Enter Global Configuration ModeAccess the switch CLI and enter global configuration mode:CodeCopySwitch> enableSwitch# configure terminalSwitch(config)# Step 2: Create a VLANUse the vlan command followed by the VLAN ID to create a new VLAN:CodeCopySwitch(config)# vlan 10Switch(config-vlan)# name SalesSwitch(config-vlan)# exit VLAN IDs can range from 1–4094 on Cisco switches .Naming the VLAN is optional but recommended for easier identification .Step 3: Assign Ports to VLANs (Access Ports)Configure individual switch ports to be members of a VLAN:CodeCopySwitch(config)# interface GigabitEthernet0/1Switch(config-if)# switchport mode accessSwitch(config-if)# switchport access vlan 10Switch(config-if)# exit switchport mode access sets the port to access mode, allowing it to carry traffic for a single VLAN .Repeat for all ports that should belong to the VLAN.Step 4: Configure Trunk Ports (Optional)If connecting multiple switches and passing multiple VLANs, configure trunk ports:CodeCopySwitch(config)# interface GigabitEthernet0/24Switch(config-if)# switchport mode trunkSwitch(config-if)# switchport trunk allowed vlan 10,20,30Switch(config-if)# exit Trunk ports carry traffic for multiple VLANs between switches .Use switchport trunk allowed vlan to specify which VLANs are permitted on the trunk.Step 5: Verify VLAN ConfigurationCheck VLANs and port assignments using:CodeCopySwitch# show vlan briefSwitch# show interfaces trunk show vlan brief lists all VLANs and their assigned ports.show interfaces trunk displays trunk port status and allowed VLANs .Best PracticesAlways create VLANs in the VLAN database before assigning ports .Use descriptive VLAN names for easier management.Keep VLAN IDs consistent across switches to avoid misconfigurations.For Layer 3 communication between VLANs, configure inter-VLAN routing on a router or Layer 3 switch .By following these steps, you can efficiently add VLANs, assign ports, and configure trunking on a core Cisco switch, ensuring proper network segmentation and traffic management.