In this guide, we will cover everything from what causes heat, to monitoring your SFP module temperatures in real time, techniques for managing heat, and preventative maintenance. And by the time you realize an SFP module has overheated, things could have already gone awry, leading to costly downtime and repairs. This condition causes laser wavelength drift, APD sensitivity degradation, and increased Bit Error Rate (BER), resulting in packet loss and TCP retransmissions in. Tried to install several SFP-modules in it. Everything is OK except the SFP modules temperature. All of them are extremely HOT after 30 secs of work. Is this normal behaviour of router or smth is going wrong? BR, Dmitry Add cooling fan to CRS-326-24P-2S+ ? Impossible to get more than 5. They're also manufactured to work in those ranges, though, so I wouldn't worry about it.