Duplex mismatch is a hidden problem on many networks. On an Ethernet network each device has a duplex setting, half or full; when two devices disagree about duplex, a duplex mismatch occurs. This degrades network performance. In business networks ISP’s usually manage routers and end users usually manage firewalls. Does either party check the duplex setting of the others device? Usually not! The result is collisions and performance issues. A typical cause of this problem is when one device (often the ISP’s router) is hard coded to full duplex and the end users device is set to auto-negotiate. One would expect the auto-negotiate setting to be capable of matching the setting of the ISP’s router, but it is not. This combination will result in a half duplex connection and less then optimum performance. Auto-negotiate works best when both devices are set in this mode. If your devices are connected to a managed switch, see how your devices are linking up to each other then correct the duplex setting if necessary. If you are NOT using a managed switch it will be more difficult to see or correct this issue.