DHCP issued by the core switch

A core switch can act as a DHCP server by configuring VLANs, SVIs, and DHCP pools, allowing connected clients on access switches to obtain IP addresses automatically.Key Configuration StepsEnable DHCP Service On Cisco switches, ensure the DHCP service is enabled using the command service dhcp in global configuration mode. This allows the switch to assign IP addresses to clients automatically .Create VLANs and SVIs Each subnet should have a corresponding VLAN and a Switched Virtual Interface (SVI) on the core switch. Assign an IP address to each SVI, which will act as the default gateway for clients in that VLAN .Configure DHCP Pools Define DHCP pools for each VLAN using the following steps:Exclude IP addresses that should not be assigned (e.g., servers, routers)Create a DHCP pool with a nameSpecify the network and subnet maskSet the default gateway (default-router)Optionally, configure DNS servers and other options like Option 150 for IP phones Trunk Links to Access Switches Ensure the links connecting the core switch to access switches are configured as trunks and carry the VLANs for which DHCP is provided. Use switchport trunk encapsulation dot1q if necessary .DHCP Relay (if needed) If clients are on VLANs not directly configured on the core switch, enable DHCP relay (ip helper-address) on the SVI to forward DHCP requests to the core switch or another DHCP server .Security and Management ConsiderationsDHCP Snooping: Enable DHCP snooping to prevent rogue DHCP servers. Mark trusted interfaces (usually uplinks to the core switch) and untrusted interfaces (end-user ports) to filter DHCP messages .Redundancy: If multiple core switches exist, ensure STP handles redundant links properly. Only one path is active at a time, but backup links can take over if the primary fails .Monitoring and Troubleshooting: Use commands like show ip dhcp binding to view assigned addresses and debug dhcp detail to troubleshoot DHCP issues .Best PracticesKeep DHCP pools aligned with VLAN subnets.Avoid overlapping IP ranges.Regularly back up the core switch configuration.Test DHCP assignments in a lab environment before deploying to production . By following these steps, a core switch can efficiently manage DHCP for all clients connected through access switches, ensuring proper IP allocation, network segmentation, and security.