There are many external factors that can cause alink failure between network appliances. Thermal, electrical/magnetic field or any harmful physical object is acommon example. On traditional layer 2 network appliances,the failover mechanism decided internally by Spanning TreeProtocol (STP) calculation. Unfortunately, in every occurrenceof failover, the communication will suffer from packet losses.When detecting a link failure, layer 2 appliances will calculate STP to decide which backup link to be selected and in that time period all of the packets suppose to be forwarded in the link will lose. On the other hand, OpenFlow capable network appliances (Software Defined Networks) can be orchestrated with a sensor to detect earlier any possible harmful external factors before a link failure happen. This initiation research only focuses to overcome an extreme thermal condition that can cause a link failure. OpenFlow Switch connected to a thermal sensor with a Raspberry Pi as a bridge. When the sensor detects temperature beyond its limit, it will tell the OpenFlow Switch to use a backup link immediately before the link failure occurs. With this mechanism packet loss can be prevented .