Q. Jumbo frames are Ethernet frames with more than 1500 bytes of payload MTU. Does Linux support jumbo frames? If so how do I set frames to 9000 bytes under Linux operating systems?
A. Most modern Linux distros (read as Linux Kernel 2.6.17+) does support frames larger than 1500 bytes. This can improve the performance. First, make sure your network driver supports custom MTU. Second you need to have a compatible gigabit NIC and switch (such as Cisco Catalyst 4000/4500 Switches with Supervisor III or Supervisor IV ) that is jumbo frame clean. If you are not sure about requirements, please refer to your product documentation.
Jumbo frames can reduce server overhead such as a big decrease in CPU usage when transferring larger file. Also you should see some increase in network throughput.
Configure eth0 interface for Jumbo Frames
WARNING! These examples may not work with your setup as it depends upon a compatible network gear such gigabit Ethernet switches and gigabit Ethernet network interface cardsSimply type the following command at a shell prompt to set new MTU (Jumbo Frames):
# ifconfig eth0 mtu 9000
Make changes permanent
Edit the network configuration file for eth0 interface - for example, /etc/sysconfig/network-script/ifcfg-eth0 (CentOS / RHEL / Fedora Linux):
# vi /etc/sysconfig/network-script/ifcfg-eth0
Append the following configuration directive, which specifies the size of the frame in bytes:
MTU 9000
A note about Debian / Ubuntu Linux user:
Debian / Ubuntu Linux user should add MTU=9000 to /etc/network/interfaces configuration file.
Close and save the file. Restart the Interface eth0:
# /etc/init.d/networking restart
To confirm the MTU used between two specific devices. use ip command as follows:
# ip route get {IP-address}
# ip route get 192.168.1.1
Output:
192.168.1.1 dev eth0 src 192.168.1.100
cache mtu 9000 advmss 1460 hoplimit 64
Application Protocol Tunning
You may need to tune the application / network protocol such as NFS and SMB to take advantage of Jumbo Frames.
Updated for accuracy.
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- Last Updated: 6-30-08
{ 6 comments… read them below or add one }
Hi, nice article
just one (1) error; for debian/ubuntu in /etc/network/interfaces, it’s mtu 9000 (mtu(space)9000) *NOT* mtu=9000 (this is only for redhat linuxes)!
Thanks for the article. I have a second ethernet card that’s a gigabit card and I tried running ifconfig eth1 mtu 9000 and it gives me an error “SIOCSIFMTU: Invalid argument”. Any idea why this is happening? Also, modifying /etc/network/interfaces didn’t seem to help either.
Chris; I just had the same thing happen on Hardy and a quick Google shows that we are not alone. It must be outside the range that our drivers/hw allow for this chipset, just taking a huge swag. I really need this to work too. FWIW:
processor : 0
vendor_id : AuthenticAMD
cpu family : 15
model : 104
model name : AMD Turion(tm) 64 X2 Mobile Technology TL-60
nVidia MCP67 Ethernet
Linux jeff-laptop 2.6.24-19-generic #1 SMP Wed Jun 18 14:43:41 UTC 2008 i686 GNU/Linux
Will get to the bottom of this since I just spent the previous weekend rewiring the house with cat6, upgraded all routers, etc….
Jeff
Follow-on to my last but just got new information. Chris, open a term and do a ’sudo ethtool eth0′ or whatever your actual device is. Amongst other useful information there was this (and yes I do have a gigabit ethernet card):
Settings for eth0:
Supported ports: [ MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Advertised auto-negotiation: Yes
Speed: 100Mb/s
Sorry if that came out dodgy but the thing to note is my driver only thinks I can do 100M and as such, I would assume it would be hard for the above command to work. Well, there is a new kernel out too so I might as well grab the drivers and make a party of it…
Jeff,
Thanks for your reply. It’s strange how you have a gigabit card, yet your limit was only 100Mb/s. Perhaps you had another one, eth1? I know mine correctly has a max limit of 1000Mb/s, but somehow I couldn’t get it to work initially. I found out my card (Netgear GA311) had a max MTU of 7500, but setting that didn’t work. When I did a little bit more googling, I found out that someone who had the same card set the MTU to 7200. Once I did that, it worked for me. So I guess your initial theory was right in that the number was out of range of the max MTU.
Hi Vivek,
What is the downside for setting higher MTU?
How would I know the proper value for MTU for my server?
I am using rhel 4 AS (2.6.9-42) , BroadCom Corporation NetXtreme II BCM5708 Gigabit Ethernet network Card and switch is 3Com® Baseline Switch 2948-SFP Plus.
Jay