Currently, informational log messages for the network component in both (mongos and mongod) are always logged.

Some users would like to disable the logging of messages such as:

2016-02-22T17:37:17.172-0600 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:64306 #2 (1 connection now open)
2016-02-22T17:38:09.376-0600 I NETWORK  [conn2] end connection 127.0.0.1:64306 (1 connection now open)

In cases where a load balancer is used, these messages yield little information and could contribute to additional IO should the connection churn be great.

Currently, the only approach is to disable logging entirely through setting quiet=true