Hello together, the problem seems to be that DELL and CISCO can't negotiate the forward error correction correctly. I had to manually set the fec to CL108-RS to be able to establish a connection. in addition I set the negotiation to off and the linkspeed to 25000. With the settings I was able to establish a connection between the DELL S5248F-On and the CISCO Catalyst 9600.Thanks for your help!
Hello together, I am trying to connect one of my DELL S5248F-ON switches to an existing network with CISCO switches. The connection should not be able to do much, it is enough if two VLANs are connected over it.Both switches (DELL and CISCO) have 25GB ports and corresponding SFP modules. The DELL switch has a SFP module from DELL and the CISCO switch has one from CISCO.Unfortunately I don't get an uplink when I connect the switches.It can't be the cable, because this cable works with the same SFP module in a DELL server without any problems. The configuration of the interface is: The status of the interface is: The line protocol is down and I don't know what the connection is missing. Is there anything I need to consider when connecting the two switches?  Thanks for your answers!  
Connection DELL S5248F-ON to Cisco switch