300-420 · Question #49
Which feature must be incorporated into the campus LAN design to enable Wake on LAN?
The correct answer is B. directed broadcasts on layer 3 devices. Wake on LAN (WoL) works by sending a 'magic packet,' which is a broadcast frame containing the target device's MAC address repeated 16 times. In a routed campus network, IP broadcasts are not forwarded across Layer 3 boundaries by default. To wake devices on a remote subnet…
Question
Which feature must be incorporated into the campus LAN design to enable Wake on LAN?
Options
- Adynamic ARP Inspection Snooping on layer 2 devices
- Bdirected broadcasts on layer 3 devices
- Cproxy ARP on layer 3 devices
- DDHCP Snooping on layer 2 devices
How the community answered
(39 responses)- A8% (3)
- B77% (30)
- C3% (1)
- D13% (5)
Explanation
Wake on LAN (WoL) works by sending a 'magic packet,' which is a broadcast frame containing the target device's MAC address repeated 16 times. In a routed campus network, IP broadcasts are not forwarded across Layer 3 boundaries by default. To wake devices on a remote subnet, the magic packet must be sent as a directed broadcast (e.g., 192.168.10.255), and the Layer 3 device (router or L3 switch) must have 'ip directed-broadcast' enabled on the destination interface so it converts the directed broadcast into a local subnet broadcast. Without this, the WoL packet cannot cross router boundaries to reach sleeping hosts on other VLANs/subnets.
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