CCNA Foundations: DHCP Relay — ip helper-address Across Subnets

Today's daily lab

Deploy a centralized DHCP service across subnets using DHCP relay (ip helper-address). A branch client on a switched LAN requests an address from a DHCP server that resides at HQ. You will configure the relay on the branch gateway, create a DHCP pool for the remote subnet on the HQ router, verify the client lease and default gateway, and test end-to-end connectivity.

Learning objectives

• Configure DHCP relay (ip helper-address) on a branch gateway for an off-subnet server.
• Build a DHCP pool on a central IOS router for a remote subnet with a correct default-router.
• Verify DHCP bindings and statistics on the server and observe the client lease.
• Validate end-to-end IP connectivity from a DHCP client to an HQ resource across routed hops.
• Troubleshoot common DHCP relay faults: wrong helper IP, missing route, incorrect pool network/mask.

Troubleshooting focus

• Client fails to obtain an IP: confirm the relay helper-address points to the reachable DHCP server IP.
• No DHCP bindings on the server: confirm the pool network/mask matches the remote client subnet and does not overlap an excluded range.
• Client gets an address but cannot reach HQ: confirm static routes between branch and HQ exist and are correct.
• Intermittent DHCP: check for mismatched subnets on the client-facing interface or unconfigured switch access VLAN mapping.