DHCP Troubleshooting Capstone: Branch Relay

Bundle lab · $29.99

Advanced CCNA troubleshooting capstone for centralized DHCP across a relay. A centralized IOS-XE router (DHCP-SRV) serves the branch LAN behind BR-RTR via ip helper-address. The lab imports in a deliberately broken state: the DHCP pool scope and gateway are misconfigured on the server, and the relay configuration is missing on BR-RTR. Learners must diagnose using show outputs and Linux tools, fix all three discrepancies, and verify that two Alpine clients dynamically receive usable leases and can reach DHCP-SRV.

Learning objectives

• Trace DHCP across a routed relay path and identify where DISCOVER frames stop
• Diagnose DHCP server pool mismatches using show ip dhcp pool and show ip dhcp binding
• Correct an IOS DHCP pool: network/mask, default-router, dns-server, domain-name, lease, and exclusions
• Enable a working DHCP relay with ip helper-address on the correct interface toward the centralized server
• Verify end-to-end success from Linux clients with udhcpc, ip addr, and ping

Troubleshooting focus

• Verify the relay path delivers broadcast requests: check for ip helper-address on the client-facing router interface
• Confirm the server has a pool whose network matches the client LAN; an off-by-one or wrong subnet prevents address assignment
• Ensure the default-router option equals the actual gateway interface IP of the client subnet
• Use show ip dhcp pool and show ip dhcp binding to corroborate pool utilization and active leases
• On clients, re-run udhcpc and confirm an in-scope address and correct default route