Hi [NAME] Law,   I'm not a networking person, but I'll try to help out. I spoke to one of my networking co-worker and did advise that it's would be good to update the switch firmware to 9.14XX as there is some issues that it can cause the settings on 10G speed, since the switch supports 10G speed networking.    Also try changing the portmode to trunk.    That's what he advised. 
Good day, Hardware: Dell S4048-ON version OS 9.11; Fortigate 200F FortiOS 6.4.7 Problem: I am unable to get a TenGigagbit port to the 4048 to establish the line protocol up. Both ends show the link is up. The switch is connected with active DAC cables to the Fortigate 200F. The cables are custom built for the correct transceivers on both ends by FS.com. Multiple cables have been tried. The S4048-ON OS 9.11 only allows setting port speed to 100 or 1000, not 10000. It assumes that 10000 is always auto-negotiate. The Fortigate port is set as a standard hardware port, with no IP address, and auto-negotiate. I'm feeling very "dense" at this point. What am I missing? Any thoughts? Thanks in advance. ------------------------------------------------------------------------------------------ S4048-ON port info: vxrsw1#show int te 1/20TenGigabitEthernet 1/20 is up, line protocol is downHardware is DellEth, address is e4:f0:04:ee:d8:26Current address is e4:f0:04:ee:d8:26Pluggable media present, SFP+ type is 10GBASE-CU2MMedium is Twinax CopperInterface index is 2099588Internet address is not setMode of IPv4 Address Assignment : NONEDHCP Client-ID :e4f004eed826MTU 1554 bytes, IP MTU 1500 bytesLineSpeed autoFlowcontrol rx off tx offARP type: ARPA, ARP Timeout 04:00:00Last clearing of "show interface" counters 43w4d1hQueueing strategy: fifoInput Statistics:5 packets, 470 bytes0 64-byte pkts, 5 over 64-byte pkts, 0 over 127-byte pkts0 over 255-byte pkts, 0 over 511-byte pkts, 0 over 1023-byte pkts5 Multicasts, 0 Broadcasts, 0 Unicasts0 runts, 0 giants, 0 throttles0 CRC, 0 overrun, 0 discardedOutput Statistics:0 packets, 0 bytes, 0 underruns0 64-byte pkts, 0 over 64-byte pkts, 0 over 127-byte pkts0 over 255-byte pkts, 0 over 511-byte pkts, 0 over 1023-byte pkts0 Multicasts, 0 Broadcasts, 0 Unicasts0 throttles, 0 discarded, 0 collisions, 0 wreddropsRate info (interval 299 seconds):Input 00.00 Mbits/sec, 0 packets/sec, 0.00% of line-rateOutput 00.00 Mbits/sec, 0 packets/sec, 0.00% of line-rateTime since last interface status change: 43w4d1h -----------------------------------------------------------------------------------------------vxrsw1#show running-config interface te 1/20!interface TenGigabitEthernet 1/20no ip addressportmode hybridswitchportno shutdownvxrsw1# --------------------------------------------------------------------------------------------------  
Line Protocol down on S4048-ON TenGigabitEthernet port- DAC Cable to Fortigate 
200D