Insight / How does LFP (Link Fault Pass Through) work on Ethernet Media Converters?
How does LFP (Link Fault Pass Through) work on Ethernet Media Converters?
August 06, 2020
James Hsiung
Application Engineer
How does LFP (Link Fault Pass Through) work on Ethernet Media Converters?

Reducing the risk of network outages is vital for critical business applications such as IP surveillance that requires 24/7 non-stop operation. Longer periods of downtime not only affects the system operation but also jeopardizes people’s safety. Therefore, to minimize such impact, LFP is necessary to constantly monitor network connectivity along with data loss prevention. This article explains how LFP works with Ethernet media converters.

What is LFP?

LFP stands for Link Fault Pass Through, which is a built-in monitoring feature in media converters that allows to constantly detect loss of signal for copper links.

Figure1. Example of Cable Breakage


Take Figure 1 for example. Without enabling LFP, both managed switch and media converter on the left side have no idea about the breakage of the copper link(Link A). Hence, Link C and Link B still continue operating despite the fact that no datacan be delivered from IP Cam.

How Does LFP Work with Ethernet Media Converters?

Example of LFP Operation

Figure2. Example of LFP Operation


LFP is able to force a media converter to shut down its fiber link in the event of a copper link breakage. Take figure 2 for example. Once LFP is enabled on both media converters, they will shut down their respective links, i.e., Link B and Link C, accordingly if Link A breaks. If SNMP (Simple Network Management Protocol) traps for link down monitoring is configured on the managed switch, an alert message will be sent out immediately from the managed switch to the NMS (Network Management System) in order to notify network engineers about any link down events. 


As network connectivity becomes so important for business, the impact of network downtime cannot be underestimated. LFP assists network engineers to quickly locate cable breakage to reduce the impact of network outages to a minimum.