[Vishal Shorghar]

Hi Dave,

You need to verify in ‘ifconfig’ command, The MTU size has been set but might not reflected in Mac GUI.

After setting up MTU=9000 through GUI as you did above, open a command terminal and try this.
#ifconfig cxgb

example: for me it works as

# ifconfig cxgb37 |grep -i MTU
cxgb37: flags=8863 mtu 9000

->Apert from these you can verify through tcpdump , if you run some traffic on Jumbo frame enabled interface, you will see bigger packets in sniffer e.g tcpdump/wireshark.

Let me know if it helps …
🙂
vishal

Mac OS x 10Gb networking engineer.