80F SFP ports

Hi all,

I have a couple of 80F i want to use as HA and uplink in FortiLink a couple of 424E switches in LAG.

I know the SFP ports are paired with WAN ports, so i switched around the physical ports (A-B to WAN, and WAN1 & 2 to FortiLink) but i can't seem to get the SFP link to go up even though the DACs are detected in the transceiver column.

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i tried forcing speed to 1gFull, to no avail. Any idea where i'm going wrong?

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https://preview.redd.it/w7pkap5herxb1.png?width=1330&format=png&auto=webp&s=a8fe8c493c67a9745b692f29513910c937b810c4