[CentOS] Jumbo frames problem with Realtek NICs?

[Christopher Chan]

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.


>
> I assumed 4K would still be better than nothing but unfortunately
> bumping up the MTU to anything else but 1.5K caused the file transfers
> (using NFS for easy testing), to hang at random points or more
> accurate slow to a crawl.

I have the crap enabled in Windows and it works there...but on an old 
server running OpenIndiana the driver refuses to enable jumbo frames for 
the particular chipset that the board has which is incidentally a 8168B.


>
> Checking the syslog, I discovered warnings that increasing MTU with
> this adapter may cause problems.
>
> Searching around, it seems to be a common problem but there doesn't
> appear to be any clear cut fix, including some suggestions to use a
> third party driver.
>
> Does anybody know of a proven solution or is the Realtek chip itself
> irrevocably broken/bugged that anything above the default 1500 will
> simply not work?

Using realtek's own drivers on Windows seem to be okay...not sure about 
Linux and other platforms.