Why AS4002T/AS4004T 10G Ethernet port not working when connecting to 2.5G network device directly?
It's a known Marvell firmware issue, the work around is connecting AS4002T/AS4004T 1G Ethernet port to the network device, then the 10G-2.5G connection will start to work.
*We'll fix it in our future software upgrade as soon as we get the firmware update from Marvell.