How to configure Jumbo Frame in SEA of VIOS ?

Jumbo Frames in VIOS

Jumbo frames are the internet packets that have payload greater than 1500 bytes. Jumbo frames are different than normal internet packets, enabling Jumbo Frame will boost the performance of LPAR during the large files transfers.

First Method making interface down

To enable jumbo frames we have to bring the interface down if its configured with an IP address
ifconfig en0 down detach

Then we need to enable the Jumbo Frames directly on physical adapter and set the mtu size to 9000
chdev -l ent0 -a jumbo_frames=yes
chdev -l en0 -a mtu=9000

Then bring the interface up by using smit mktcpip and select the en0 click enable the interface to start.

Second Method this requires VIOS reboot

To enable the Jumbo Frame while interface is running please use the below command

chdev -l ent0 -a jumbo_frames=yes -P

The option -P force enables the interface until next reboot. So to enable the Jumbo Frame you will have to require the VIOS reboot

reboot

Once reboot is done you will be able to see the Jumbo Frame settings

Verifying the Jumbo Frames

To verify the Jumbo Frame setting we need to run list attributes over the adapter ent0. It will list out the settings and to list the interface en0 mtu size.

# lsattr -El ent0 | grep jumbo
jumbo_frames     yes/True

# lsattr -El en0 | grep -i mtu
mtu=9000

Once the interface is up try to ping the LPAR with 8000 bytes of payload that has already enabled Jumbo Frames

ping -s 8000 partition1

Ping should be successful. If ping fails are you see the packet loss then contact system admin to enable the Jumbo Frame over the switch. Ping may be failed due to another reason where ping target may not have enabled the Jumbo Frame, make sure Jumbo Frame settings are enabled over partition1 LPAR as well.

To read more about how to troubleshoot the Jumbo Frames interface click here


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