Configuration from Core Switch to Router

To connect a core switch to a router, configure VLANs, trunking, IP addresses, and routing protocols to enable communication between subnets and ensure efficient network traffic flow.Step 1: Physical ConnectionConnect the core switch to the router using a physical Ethernet cable. Ensure the interfaces on both devices are operational and compatible with the intended speed and duplex settings .Step 2: IP Address ConfigurationAssign IP addresses and subnet masks to the interfaces on both the core switch and the router that are directly connected. This allows the devices to communicate at Layer 3 .Step 3: VLAN CreationCreate VLANs (Virtual LANs) on the core switch to segment the network into logical subnets. For each VLAN:Assign a VLAN ID and name.Configure VLAN interfaces (VLANIF) and bind them to the VLAN .Assign switch ports to the appropriate VLANs as access ports.Step 4: Trunk ConfigurationConfigure trunk ports on both the core switch and the router interfaces that carry multiple VLANs. Use 802.1Q encapsulation to allow VLAN traffic to pass through the trunk .Step 5: Routing ProtocolsEnable routing protocols on the router to allow dynamic routing between VLANs and external networks. Common protocols include:RIPOSPFEIGRP Configure the router to advertise the VLAN subnets and ensure the core switch can forward traffic appropriately .Step 6: VPN and Security (Optional)For enterprise environments, configure VPN instances on the core switch to isolate traffic between public networks, firewalls, and egress routers. Bind VLANIF interfaces to the VPN instance to maintain secure routing .Step 7: VerificationVerify connectivity and proper configuration:Use ping to test communication between VLANs and the router.Use show vlan brief and show ip route commands to confirm VLANs and routing tables are correctly configured .Check trunk status with show interfaces trunk to ensure VLAN traffic is passing correctly.Step 8: Best PracticesUse consistent naming conventions for VLANs and interfaces.Document IP addressing and VLAN assignments.Regularly back up switch and router configurations.Monitor network traffic to detect misconfigurations or bottlenecks. By following these steps, the core switch and router will be properly configured to handle inter-VLAN routing, efficient traffic management, and scalable network growth .