[CentOS] Jumbo frames problem with Realtek NICs?

Emmanuel Noobadmin centos.admin at gmail.com
Sat Jun 25 19:05:31 UTC 2011


On 6/26/11, Gordon Messmer <yinyang at eburg.com> wrote:

> I don't know anything specifically about those cards, but you'll see
> that behavior on any card unless all of the hosts on a broadcast domain
> are using the same MTU.  You need to set all of the devices on a LAN
> segment, including the router, to the same MTU.

Thanks for this note, but it didn't seem to be necessary in my case.

I just finished updating the drivers and running some test, the
results were this.

In all cases, default 1500 MTU to 1500MTU = OK for both default and
Elrepo drivers.

NFS Host -> NFS Client
Default Drivers for both
1500 MTU -> 3000 MTU = fail
3000 MTU -> 3000 MTU = fail

Default Driver -> ElRepo driver
1500 MTU -> 3000 MTU = OK
3000 MTU -> x MTU = fail

ElRepo -> ElRepo driver
Both OK

So the MTU problem appears to be firmly pinpointed to the default RTL
drivers and both receiving/transmitting NICs must be using the ElRepo
drivers to work properly at higher MTU.

Ironically, even at 1500MTU, I was able to hit the full 100+ MB/s
speed available on a single Gigabit link so it seems my experiment was
a bit futile.



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