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How to change the flow control and MTU settings on physical interfaces with minimum disruption in a production environment

Last Updated:

Applies to

  • Data ONTAP 8.1 7-Mode 
  • OnCommand System Manager 
  • Data ONTAP 7 and earlier 


When physical interfaces are part of a logical interface such as a VIF or IFGRP, the MTU and flow control settings cannot be modified. Due to this, you must either disruptively destroy the logical interface and make the changes with the ifconfig command and change the /etc/rc file or non-disruptively change the /etc/rc file and perform a takeover and giveback. The cf takeover and cf giveback commands can be used to make changes to interface groups in the HA pair in a non-disruptive manner. For more information, see Making nondisruptive changes to the interface groups

Change the configuration of the /etc/rc file, so that a file can be read and the interfaces are configured in order to reflect the new MTU size and flowcontrol settings the next time, as shown in the following example. The MTU and/or flowcontrol setting should be modified prior to the creation and configuration of the logical interface.

Note: Applying the below configuration will result in OnCommand System Manager (OCSM) presenting the following message on clicking Network Interfaces:

Active operations on network interfaces are disabled because the /etc/rc file does not adhere to the format supported by System Manager. Modify the /etc/rc manually to enable the active operations.

This is expected per OCSM Documented Issue 810865.  The /etc/rc file must henceforth be modified manually.

NOTE: In Clustered Data ontap, modifications to Flow Control or MTU will result in a several second interruptions of service on the specific network port.



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