[CentOS] Jumbo frames problem with Realtek NICs?

[Ljubomir Ljubojevic]

Christopher Chan wrote:
> On Friday, June 24, 2011 02:33 PM, Emmanuel Noobadmin wrote:
>> On 6/24/11, Christopher Chan<christopher.chan at bradbury.edu.hk>  wrote:
>>> On Friday, June 24, 2011 01:20 AM, Emmanuel Noobadmin wrote:
>>>> First bottleneck was discovering the max MTU allowed on these is 7K
>>>> instead of 9K but googling seems to indicate that the RTL8168B is only
>>>> capable of 4K frames.
>>> Yeah, the 8168C goes up to 7k. Some 8168B go up to 6k.
>> In cases like this where there are conflicting sources of information
>> regarding the max MTU of a NIC, what would be the correct way to
>> determine the actual max MTU? I figured the 7K limit basically by
>> doing a binary search with the ifconfig mtu commands. But is the this
>> figure simply what the driver will accept for the controller it
>> identified or is that the actual hardware limit?
> 
> Given that these are the limits from Realtek's own Windows drivers, I'd 
> say they are hardware limits and different from chipset/rev.



This post:
http://ubuntuforums.org/showthread.php?t=1628575
Suggests that Windows and OpenSolaris were pusing 3x more then his 
current Ubuntu. This would suggest Linux driver problem. That is why I 
suggested ElRepo driver.

I just checked my server and my desktop. They both have 8168B NIC. 
Server integrated and desktop has PCI-X if I am not mistaken (I on 
laptop 35km away) with what seams to be stock kernel driver r8169.

When I first bought Gigabit switch (cheap Intex) they were both plugged 
next to each other. CentOS -> CentOS NFSv4 large files copy gave me 
sustained speed of ~250Mbps (~31 MBps), without even touching the 
settings, which is good for HDD(s) I had back then.

I can not comment on JUMBO frames, never needed them. But it would be 
nice to see if there is difference with ElRepo drivers.

Ljubomir