Linux - Networking This forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game. |
Notices |
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
Are you new to LinuxQuestions.org? Visit the following links:
Site Howto |
Site FAQ |
Sitemap |
Register Now
If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here.
Having a problem logging in? Please visit this page to clear all LQ-related cookies.
Get a virtual cloud desktop with the Linux distro that you want in less than five minutes with Shells! With over 10 pre-installed distros to choose from, the worry-free installation life is here! Whether you are a digital nomad or just looking for flexibility, Shells can put your Linux machine on the device that you want to use.
Exclusive for LQ members, get up to 45% off per month. Click here for more info.
|
 |
07-31-2013, 11:12 PM
|
#1
|
Member
Registered: Aug 2011
Location: USA
Distribution: ArchLinux - 3.0 kernel
Posts: 349
Rep: 
|
iperf hangs when jumbo frames are enabled
i've enabled jumbo frames on 2 linux machines by using "ifconfig ethX mtu 9000". Running "iperf -s" seems to work normally, but when I try to do an iperf test via "iperf -c x.x.x.x" from the other jumbo-enabled Linux machine, it just hangs forever; no command output, and of course nothing in any logs. Trying this:
Code:
iperf -c x.x.x.x -M 9000
yields this:
Code:
WARNING: attempt to set TCP maximum segment size to 9000, but got 536
all other network transfers of any kind work fine, it's just iperf that doesn't. any ideas?
thanks
|
|
|
08-01-2013, 05:50 PM
|
#2
|
Senior Member
Registered: Jan 2012
Distribution: Slackware
Posts: 3,348
Rep: 
|
Quote:
Originally Posted by psycroptic
Code:
iperf -c x.x.x.x -M 9000
|
The -M parameter specifies the TCP Maximum Segment Size. This does not include the IP header, so you've just told iperf to generate 9040 byte packets, which are larger than the MTU.
That would explain this:
Quote:
Originally Posted by psycroptic
Code:
WARNING: attempt to set TCP maximum segment size to 9000, but got 536
|
Not sure why it defaults to 536, but you should try iperf -c x.x.x.x -M 8960 and see what happens.
|
|
|
08-01-2013, 06:00 PM
|
#3
|
Member
Registered: Aug 2011
Location: USA
Distribution: ArchLinux - 3.0 kernel
Posts: 349
Original Poster
Rep: 
|
Doing that produces the same warning. Actually, I can't seem to set the -M value to anything BUT 536. Anything below or above gives the error. strange... maybe this version of iperf isn't built to handle non-default segment sizes?
|
|
|
08-01-2013, 06:14 PM
|
#4
|
Senior Member
Registered: Jan 2012
Distribution: Slackware
Posts: 3,348
Rep: 
|
That is entirely possible, but I haven't seen any other complaints about this. Are you sure the link speed on the NIC is actually 1 Gbps?
I just noticed that you're running iperf and not the newer iperf3. I just downloaded the latest version, and the -M 8960 parameter didn't return an error.
|
|
|
08-01-2013, 06:23 PM
|
#5
|
Member
Registered: Aug 2011
Location: USA
Distribution: ArchLinux - 3.0 kernel
Posts: 349
Original Poster
Rep: 
|
Quote:
Originally Posted by Ser Olmy
Are you sure the link speed on the NIC is actually 1 Gbps?
|
Absolutely, here's a relevant line from lshw:
Code:
configuration: autonegotiation=on broadcast=yes driver=e1000e driverversion=2.3.2-k duplex=full firmware=1.8-0 ip=x.x.x.x latency=0 link=yes multicast=yes port=twisted pair speed=1Gbit/s
i'll check out iperf3, thanks
|
|
|
All times are GMT -5. The time now is 12:17 PM.
|
LinuxQuestions.org is looking for people interested in writing
Editorials, Articles, Reviews, and more. If you'd like to contribute
content, let us know.
|
Latest Threads
LQ News
|
|