Which two types of 100G router interface does pre-FEC proactive protection work on? (Choose two.)

Question

Options

• AIP-over-DWDM
• Bgray plus transponder
• CPacket-over-SONET
• DWAN PHY

• A
  74% (14)
• C
  16% (3)
• D
  11% (2)

Explanation

Pre-FEC proactive protection monitors the bit error rate before Forward Error Correction is applied, enabling traffic switchover before a link actually fails. This requires the router interface to have visibility into FEC processing - which only occurs on IP-over-DWDM (coherent optical interfaces with integrated DWDM capabilities) and gray plus transponder setups (where the external transponder performs FEC and passes pre-FEC BER data back to the router). Both interface types sit in the DWDM optical domain where FEC is inherent to signal transport.

Packet-over-SONET (C) uses SONET framing and its own overhead for error management - it doesn't participate in the FEC-based optical monitoring chain that pre-FEC protection depends on. WAN PHY (D) maps Ethernet into SONET-like framing and is typically associated with 10GbE, not 100G coherent optics, so it also lacks the pre-FEC BER signal path.

Memory tip: Ask yourself - "Is FEC happening in the optical layer here?" If yes (coherent DWDM built-in, or a transponder doing it externally), pre-FEC protection can work. If the interface is SONET-framed or PHY-layer Ethernet without coherent optics, there's no pre-FEC signal to monitor.

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