Intel CT Desktop Adapter (82574L) jumbo frames

Aug 2, 2012
Supermicro X8DA6
X5690 x 2
RX 580
Mobile Phone
Intel CT Desktop Adapter EXPI9301CT (82574L) installed on multiple hacks (Z77X-UP5TH, X58A_UD3R, AsusP5Q). Adapters are working fine either with Hnak AppleIntelE1000e or edited Intel82574L kext. They are on separate network, W/O internet access, connected to NAS, delivering 110 Mb/s write & 111 Mb/s read ..... and that's great.
However, from specific reason, I would like to have jumbo frames enabled:
- MTU set to 9000, after 30 seconds connection drops off. In system preferences it says that adapter is connected and working, but it is not and I can not access any shares.
- MTU set to 4000. Connection stays on, according to Blackmagic Disk Speed Test I have 115 Mb/s write but 0 read.
In order to rule out errors in other network equipement I have tried:
- Connecting through managed switch to 4 port link aggregated NAS (4 port Intel server adapter on Debian Linux)
- Connecting directly to one port on NAS
- Connecting two hacks with Intel CT Desktop Adapter directly

Results are always the same as described above, so conclusion is that error is somewhere in OSX driver or some specific settings. According to older threads it looks like that some users actually have jumbo frames enabled, without any issues?
Any help would be greatly appreciated!