On 11/09/2015 12:36 PM, Gordon Messmer wrote:

On 11/09/2015 08:34 AM, Steve Clark wrote:

...

Has anyone using CentOS 6 been able to successfully set an mtu larger than 9710 on an interface.

Maximum frame size varies from implementation to implementation: http://pages.uoregon.edu/joe/jumbo-clean-gear.html

It's also worth noting that that due to offloading features in modern NICs, there's often very little benefit to large frames. Since you *really* need all of the devices on any network segment to use the same MTU, the best option might be to eliminate jumbo frames (and test the impact of doing so in terms of throughput and CPU utilization).

Hi Gordon,

Thanks for the response.

The real issue relates to doing pcap on an interface that is hooked to a span port. The super jumbo frames cause rx_long_length_errors: 2701813 which show up in our monitoring software and the customer thinks there are error on his network.

So I wanted to increase the mtu on the interface so these errors would not be reported.

On 11/9/2015 9:57 AM, Steve Clark wrote:

The real issue relates to doing pcap on an interface that is hooked to a span port. The super jumbo frames cause rx_long_length_errors: 2701813 which show up in our monitoring software and the customer thinks there are error on his network.

So I wanted to increase the mtu on the interface so these errors would not be reported.

9K or so is the upper limit for MTU on most NIC cards, and many are less than that. this is a hardware thing, has nothign to do with software.