Cascading between a FortSwitch 124F and a Zyxel GS220-50

Dear Sir/Madam,

I am experiencing difficulties establishing cascading between a FortSwitch 124F and a Zyxel GS220-50 using the SFP/GBIC ports. During testing, we identified that the Zyxel's SFP port is only negotiating 100 Mb, which prevents communication with the FortSwitch, which requires a minimum negotiation of 1 Gb.

Below is a summary of the diagnosis already performed by the TeleData technician:

The FortSwitch 124F is operating normally; the parameters have already been adjusted to speed 1000/full and inspections have been removed.

The GBICs were tested on other switches (TP-Link and Cisco) and negotiated 1 Gb normally, ruling out physical defects in the modules.

On the Zyxel GS220-50, SFP port 47 remains negotiating at only 100 Mb, even when using a 1 Gb GBIC.

SFP ports 49 and 50 were also tested; however, no LEDs light up and the negotiation does not increase to 1 Gb.

The VLANs on the FortSwitch are correct, with the port configured to pass the local VLAN (untag).

Current suspicion: possible limitation or configuration on the GS220-50 that is restricting the negotiation of the SFP ports.