F5 error layer 2

Dear all

I had a problem with f5 device. I had connected a cable between Port 1.5 BIG-IP-01 with 1.5 BIG-IP-02. The Led had Green but I had checked on GUI both interface had DOWN status. Configure of 2 interfaces is default.

Then I had tested with port 1.6 BIG-IP-01 with 1.6 BIG-IP-02 and the same result.

How to fis it?

Best regards

vhv84