Skip to main content
rmatt
New Member
August 25, 2016
Question

Fortigate 300 D and Cisco 3750X SFP connection

  • August 25, 2016
  • 3 replies
  • 9379 views

Hello All,

 

I'm trying to connect the 300D to a Cisco 3750x to the SFP ports. It has this module C3KX-NM-10G which allows for 2 10GB or 4 1GB connections. G1 is in use and working. I'm using a twinax cable to make the connection, SFP-H10GB-CU1M=. If i plug it into G2 (cisco) and port5 (300D) I get link light on the 300D but not the Cisco. If I put it in G3, I get port error disabled on the Cisco side, usually this is due to a duplex or speed mismatch but I can't force a speed or duplex on these module SFP ports. I have tried setting this up as a trunk line and as just regular access, also tried assigning it an independent IP nothing seems to change. Is the twinax cable the problem or is it a config issue on either side? Anyone else have the 300d working with a twinax cable?

 

Thanks

3 replies

MrSinners
New Member
August 26, 2016

There are two things that are odd about this, first the usage of a 10GB cable and SFP's, while the 300D only has 1GB ports. Secondly, speed is something that can be set to a fixed speed on the FG or did you mean the switch where it is not possible to set?

 

Also, sometimes other vendor SFP's do not work on a FortiGate and is not recommended as a best practice. I have seen Cisco and Checkpoint SFP's work in a Fortigate, but also a few Cisco SFP's that did not work.

ede_pfau
SuperUser
SuperUser
August 26, 2016

In my experience the FGT SFP or SFP+ ports do not auto-negotiate speed (duplex always is full duplex with fiber). Try to nail it to 1000M, even if the Cisco doesn't support fixed speed on these ports (really?).

Thought Leadership Security Summit. Outpace New Threats with AI - enhanced defense. Tuesday, Septmeber 15, 8:30 AM - 2:30 PM PT. The Golf Club at Newcastle, WA.
Virtual event | September 2026. SASE summit. The age of autonomous trust. Register here!