Connecting ICX7450 to Mellanox switch

[SteelyBran]

We're working on connecting a Brocade ICX7450 to a Mellanox switch that came with a new virtual host.  We're able to connect to the Mellanox using a management connection directly into one of the ethernet ports on the Brocade, but the fiber connection does not appear to be passing any traffic (we can see on both that the connection is physically detected).  We have the port on the Brocade in Dual mode on our default VLAN and tagged on several VLANs on the port connecting the two, but nothing seems capable of hitting the Mellanox or the server connected directly to it.  The various server nodes connected to the Mellanox can ping each other.  
I can see the physical connection between the devices in the web interface as well as link lights on both, and can see packets going across.  I've tried different SFP modules and a different fiber cable to eliminate those as possibilities.