Broadcast Time on a Shared LAN

Bundle lab · $29.99

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