Need help getting Forti Products to talk to Dell N1548P switches

Forum|Forum|13 days ago
May 26, 2026
3 replies
100 views

I’m kind of at a loss as to how to make this work. I’m configuring a new FortiGate 90G, and what I’d like to do is connect a cable to an access port on my existing Dell network to a WAN port on the firewall, so it can get a DHCP IP, so I can register it. The problem is that I can’t get layer 1 to work at all. No link lights. I plug a PC into the same cable; it gets an IP just fine. The cable works. The Dell switch works. The FortiGate is brand new out of the box. I had the exact same issue when I was configuring my new 120G firewalls as well. Here’s something weird. I can connect a dumb unmanaged 5 port switch in between the Dell and the FortiGate, and everything connects and works perfectly fine. The firewall gets an IP perfectly fine. I disconnect the unmanaged switch, and go straight from the Dell to the FortiGate, and I get nothing. I’ve been on this for weeks, with no resolution, or even understanding, as to why this is happening. I’ve also tried putting a FortiSwitch inline between them and I can’t get link lights between the FortiSwitch and the Dell N1548P either. I’ve configured both ends, and nothing. No link lights. Any clues from people way smarter than me?

Toshi_Esumi

SuperUser

I’m assuming the dumb switch you tried was 10/100/1000Base-T switch connected to Dell’s one of 10/100/1000Base-T ports.
First thing I would try is to set the FGT’s wan port to be “1000auto”. Then if still doesn’t work, I would try shutting down POE on the Dell’s port (“power inline disable”?). I don’t have either G-series FGT or Dell switch. So I don’t know the exact command lines.

Toshi

D

dejjenAuthor

New Member

I’ve tried manually manipulating the speed and duplex settings on both sides. It did not fix it. I also turned off inline power, and still nothing.

J

Josué Pisté Chan Monedero ALTE

New Member

It seems more like a physical negotiation issue (speed/duplex/autonegotiation) between the Dell and the FortiGate ports than a firewall or cable failure, especially since it works when an intermediate switch is used. The unmanaged switch is likely renegotiating compatible parameters between the two devices.

Some things I would try:

Check if the Dell ports are forced to 1G/10G or have specific autonegotiation settings.

Manually force the speed and duplex on both the switch port and the FortiGate's WAN port to test compatibility.

Check if EEE (Energy Efficient Ethernet/Green Ethernet) is enabled on the Dell; it can cause problems with some devices.

Confirm if the FortiGate port uses RJ45 or SFP and if there are any supported speed limitations.

Update the FortiGate firmware if it came with an older version from the factory.

Review the Dell logs to see if it detects connection attempts or physical errors.

The fact that this also happens with a FortiSwitch in the middle of the Dell suggests a negotiation incompatibility with the N1548P's ports, rather than a defect in the FortiGate. What speed/configuration is the Dell's port currently running?

D

dejjenAuthor

New Member

I didn’t mean to imply that the FortiGate was faulty. It does appear to be on the Dell end. I’ve tried to manually set speed/duplex on both ends with no luck. I turned off the eee on the interface as well. Both ends are RJ45. I need to get the FortiGate online before I can register the device and download firmware. There is nothing showing in the dell logs. Dell is currently set at auto negotiate, but I have tried forcing it to 1000/full with no resolution.

Toshi_Esumi

SuperUser

You mentioned nothing in Dell’s log. How about FGT side, nothing is there either?
Since you said no log on Dell, it’s unlikely. But make sure STP is not in blocking state on the port.

Toshi

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