Applies to:
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Operating Systems: Enterprise Linux 4.x, 5.x
 

Problem:
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How do I enable Jumbo Frames on my servers?


Solution:
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There are a number of ways to accomplish the task of configuring Jumbo Frames on an Enterprise Linux server, the following is simply the Dell recommended best practice. The iproute2 method is preferred to the older slightly deprecated net-tools methods.

NOTE: These steps will need to be done on each interface that need Jumbo Frames enabled.

Issue the following command:       
ip addr show eth0

This will produce output similar to:       
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq qlen 1000
link/ether 00:15:c5:f1:45:8d brd ff:ff:ff:ff:ff:ff
inet 172.16.4.10/16 brd 172.16.255.255 scope global eth0

Run the following command the change the MTU size of the device which will effectively enable JumboFrames for the device:
ip link set eth0 mtu 9000
   
Now we will re-run the original command:
ip addr show eth0
   
This will produce similar output to the following, taking note of the listing of the mtu:
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc mq qlen 1000
link/ether 00:15:c5:f1:45:8d brd ff:ff:ff:ff:ff:ff
inet 172.16.4.10/16 brd 172.16.255.255 scope global eth0

At this point we will need to set this to be persistent accross reboots using the network scripts. For the example so far we have used the eth0 interface and will continue to do so here, change eth0 to the interface name needed for your system configuration. Edit the /etc/sysconfig/network-scripts/ifcfg-eth0 file with your favorite editor and add the following line:
MTU=9000           

NOTE: Make sure ONBOOT=yes is also on a line in the /etc/sysconfig/network-scripts/ifcfg-eth0 file and that the command "chkconfig --list network" shows the service to be enabled for the appropriate runlevels. This will ensure the device will come up on next reboot.