Why does the network interface gets disconnect randomly ?

Issue

• Its seen the system is disconnecting interface for no apparent reason. Log shows: kernel: igb 0000:01:00.1: em3: igb: em3 NIC Link is Down
• While there is no connection, ethtool reports:

Settings for em3:
        [...]
        Link detected: no

• Finally, when running ifconfig em3 down followed by ifconfig em3 up and then checking ethtool again provides following ouput:

Settings for em3:
    [...]
    Link detected: yes