Procedure:AIX jumbo frames

How to configure jumbo frames (>1500 byte MTU) under AIX

Note: The interface must be down and unconfigured in order to change the ethernet adapter hardware characteristics. You must be accessing the system via a local console or secondary network interface in order to make these changes.

1. Log into the AIX system, and start SMIT
2. In SMIT, select the following menu items:
   • Devices
   • Communication
   • Ethernet Adapter
   • Adapter
   • Change / Show Characteristics of an Ethernet Adapter
   • Select the interface in question from the list
3. Change Transmit jumbo frames to 'yes'
4. Press 'enter' to make the change
5. Hit F3 or <esc>3 until you're back out to the main menu (System Management)
6. Select the following menu items:
   • Communications Applications and Services
   • TCP/IP
   • Further Configuration
   • Network Interfaces
   • Network Interface Drivers
   • Select the interface in question from the list
   • Ensure that Maximum IP PACKET SIZE for THIS DEVICE is set to '9000'

Command line

The following two operations will make the above changes, but also require a reboot to effect. The plus side is you can do them while the interface is up.

Replace ent2/en2 in the example with the device names required on your system - ie, ent1/en1 on the JS20s.

chdev -Pl ent2 -a jumbo_frames=yes
chdev -Pl en2  -a mtu=9000