I would presume it is as far as a networking standard. They would be compatible, however in performance, you'll take a big hit if you directly connect the 345 to the 685 as the Max supported speed connections on the 685 I believe is only 100Mb. I would check the specs on the 685 and see. The 345 is Gb supporting so if you do want to do this, I would recommend getting an external network Gb switch to add between the 685 and the 345. This is preferred as well.