IntermediatePublished 2026-07-04
Broadcast Time on a Shared LAN
Bundle lab
Lab 5 of 10 in NTP & Network Time · ← Previous · Next →
CCNA exam domain: IP Services
Configure a deterministic NTP broadcast design on a single shared LAN. R1 acts as an authoritative clock (ntp master 3) and broadcasts time on its LAN interface. R2 and R3 act as broadcast clients to scale time distribution without per-client server statements. Verify broadcast associations on the clients and understand the tradeoffs vs. unicast client/server.
Learning objectives
- Configure an IOS router as an authoritative NTP master at a chosen stratum
- Enable NTP broadcast on a LAN interface and configure clients to listen
- Verify broadcast associations and status on NTP clients
- Discuss scaling and accuracy tradeoffs of broadcast vs. unicast NTP
- Operate without routing or multiple subnets: one shared LAN segment only
Troubleshooting focus
- Clients do not show a broadcast association due to missing 'ntp broadcast client' on the correct interface
- Server is not authoritative (missing 'ntp master <stratum>') so clients never settle on a source
- Interface mismatch or shutdown prevents LAN broadcasts from reaching clients
- Mask/address mismatch breaks ARP on the flat subnet
- Accidentally adding 'ntp server' overrides the broadcast test plan
Topology
Subscribe to preview this lab's topology.
See plansGrade your work
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.
- Scored something you believe is correct? Use Report an issue on this page — that is exactly how the grading fixes in the changelog got found.
Create a free account to submit your lab for grading.
Create a free accountFound a problem with this lab?
Please sign in to report a problem — tying it to your attempts lets us reproduce and fix it faster.