Do I have to add a mezzanine card to each compute module?
One Dual Gigabit Ethernet I/O Expansion Mezzanine Card AXXGBIOMEZ is required for each compute module that needs to access the second switch.
What kind of compute modules are in the MFSYS35, and have you added a mezzanine card to each?
(info from Intel® Modular Server System MFSYS25 — FAQs about the Intel® Gigabit Ethernet Switch AXXSW1GB )