Why is auto-negotiation relevant to a discussion of network taps or Data Access Switches?
All Gigabit capable copper taps negotiate, establish and maintain two separate links between the tap and the endpoint devices of the link. If one link endpoint device is only 10/100 capable and the other endpoint is 10/100/1000 capable then the taps respective tap assembly ports will each negotiate to the highest available speed – resulting in a speed mismatch and significant performance issues on the link. The required solution is to hard set the ports of both the endpoint devices and the tap assembly to fixed speed and duplex settings. Data Access Switch products, although they are not subject to the speed mismatch issue because they are not used in-line, can face a different challenge. If simple non-aggregating passive fiber taps are used as the source of data to provide inputs to a Data Access Switch then the ports on that device must have Auto-negotiation disabled in order to accept data. But if other ports on that same device are used to accept data from SPAN ports or aggregation