Multiple VLANs on the core switch

To implement multiple VLANs on a core switch, configure VLANs on the core, use trunk ports to connect to other switches, and optionally use VTP for centralized VLAN management.VLAN Creation and AssignmentStart by creating VLANs on the core switch using the vlan command in global configuration mode. Each VLAN should have a unique VLAN ID and name. Assign VLANs to switch ports using switchport access vlan for access ports connected to end devices. For ports connecting to other switches, configure them as trunk ports using switchport mode trunk to carry multiple VLANs across switches .Trunking Between SwitchesTrunk ports allow multiple VLANs to traverse a single link between switches. Ensure that all inter-switch links are set to trunk mode and allow the necessary VLANs. This enables devices in the same VLAN on different switches to communicate seamlessly . Use Gigabit ports for uplinks to improve bandwidth and stability, and standard Cat5e or better cables are sufficient for these connections .VLAN Propagation with VTPFor Cisco switches, you can use VLAN Trunking Protocol (VTP) to centralize VLAN management. Configure the core switch as the VTP server and other switches as VTP clients. This ensures that any VLAN changes on the core switch automatically propagate to all client switches in the same VTP domain .Inter-VLAN RoutingIf devices in different VLANs need to communicate, configure a Layer 3 interface (SVI) on the core switch for each VLAN. Assign an IP address to each SVI to act as the default gateway for devices in that VLAN. Ensure that the trunk ports carry the VLANs to the core switch so routing can occur centrally .DHCP ConsiderationsFor multiple VLANs, DHCP requests are broadcast within a VLAN. To provide IP addresses across VLANs, either configure a DHCP server on the core switch or use a router with DHCP relay (IP helper) to forward requests from each VLAN to the DHCP server . Each VLAN should have its own subnet to avoid conflicts.Best PracticesEnable Spanning Tree Protocol (STP) to prevent loops in the network.Use separate VLANs for different departments or services to improve security and reduce broadcast domains.Limit VLANs on trunk ports to only those required to reduce unnecessary traffic.Document VLAN IDs, names, and IP subnets for easier management. By following these steps, you can successfully configure multiple VLANs on a core switch, ensure proper inter-switch communication, and maintain efficient network segmentation and routing.