Why the NIC's link using 'igb' module goes down intermediately ?

Issue

• In working condition, suddenly the NIC link goes down as shown in below logs and there is no relevant log/message before link down log to understand why the link is going down.

Jul  7 12:16:37 HOSTNAME postgres[29722]: [7-1] [29722 - 0] LOG:  duration: 4672.672 ms  statement: EXECUTE <unnamed>  [PREPARE:  COMMIT]
Jul  7 12:16:37 HOSTNAME postgres[30298]: [4-1] [30298 - 0] LOG:  duration: 3926.874 ms  statement: EXECUTE <unnamed>  [PREPARE:  COMMIT]
Jul  7 12:16:37 HOSTNAME postgres[29721]: [8-1] [29721 - 0] LOG:  duration: 2930.924 ms  statement: EXECUTE <unnamed>  [PREPARE:  COMMIT]
Jul  7 12:16:46 HOSTNAME kernel: igb: ethbx1 NIC Link is Down        <<<-------
Jul  7 12:16:47 HOSTNAME postgres[30299]: [6-1] [30299 - 0] LOG:  duration: 2579.886 ms  statement: EXECUTE <unnamed>  [PREPARE:  COMMIT]
Jul  7 12:16:47 HOSTNAME postgres[29721]: [9-1] [29721 - 0] LOG:  duration: 2443.066 ms  statement: EXECUTE <unnamed>  [PREPARE:  COMMIT]

• When link goes down, ifup/ifdown is executed on that particular interface to make it up and working again.

Jul 11 20:06:48 HOSTNAME postgres[12083]: [2-1] [12083 - 0] LOG:  connection authorized: user=emarsys database=budb
Jul 11 20:06:48 HOSTNAME postgres[12084]: [2-1] [12084 - 0] LOG:  connection authorized: user=emarsys database=budb
Jul 11 20:07:13 HOSTNAME kernel: igb: ethbx1 NIC Link is Down             <<<------
Jul 11 20:07:22 HOSTNAME postgres[12495]: [1-1] [12495 - 0] LOG:  connection received: host=<IP> port=59382
Jul 11 20:07:22 HOSTNAME postgres[12495]: [2-1] [12495 - 0] LOG:  connection authorized: user=postgres database=template1