IntermediatePublished 2026-08-27
CCNA Break/Fix: The DHCP Request That Goes Nowhere
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Lab 4 of 7 in CCNA Break/Fix: Diagnose and Repair · ← Previous · Next →
Branch staff cannot work: no workstation on the user LAN holds an address. By design, clients there lease from the hub router's scope and the two sites route to each other statically. Find why no lease arrives; change nothing else.
Learning objectives
- Trace a DHCP exchange between a client and an off-subnet server
- Distinguish a reachable peer from a working service
- Isolate a failing DHCP path hop by hop
- Diagnose an empty binding table against what each hop shows
- Verify CLIENT-BR holds a lease in 10.10.10.0/24
Troubleshooting focus
- CLIENT-BR holds no address and keeps retrying. Run
udhcpc -i eth0 -nin the foreground to watch it discover, and again after each change. - The client gets nothing while RTR-BR and RTR-HUB ping each other cleanly over the /30. A working transit link is not evidence a DHCP exchange crosses it.
show ip dhcp bindingon RTR-HUB stays empty. That is an observation, not a verdict; narrow it withshow ip route,show ip interfaceanddebug ip dhcp server packet.- Every interface along the path reads up and the routers log no error, yet no lease appears. A relay path fails silently at whichever hop drops it; watch both routers with
debug ip udpwhile the client retries.
Topology
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How this lab is graded
- Build it your way. Where a lab lets you choose a value — a VLAN name, an interface description — grading checks that you configured it, not which name you picked. Names that another line has to reference, like an ACL applied with
access-class, are stated in the guide and do have to match. - Addresses, modes and protocol keywords are exact. An IP address, a subnet mask,
switchport mode trunk, an encapsulation — these carry the meaning of the lab, so they are graded as written in the guide. - Grading reads your saved configuration. Export the lab from CML after you have configured it, and make sure anything you set is in the
running-config— a change that only exists in a terminal session never reaches the grader. - You can submit as many times as you like. Your best score stands, and each attempt tells you which checks passed so you can work the gaps.
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