Switches allow for what type of duplexing

The mode can be modified to correspond with each specific type of communication program. When set to a half-duplex system, connections alternate use of the communication channel and hardware can determine the time each data link in the system is allotted for transmissions.

There are distinct differences between full and half-duplex systems. With half-duplex mode, each transmitted character is immediately displayed on a monitor. Each NIC and switch port has a duplex setting.

For all links between hosts and switches, or between switches, the full-duplex mode should be used. However, for all links connected to a LAN hub, the half-duplex mode should be used in order to prevent a duplex mismatch that could decrease network performance. In Windows, you can set up duplex settings in the Properties window of your network adapter:. Ethernet ports on Catalyst switches have built-in on-board Ethernet transceivers. Devices that connect to Ethernet ports might have on-board Ethernet transceivers or use external transceivers.

Straight-through means that pin 1 on one end of the cable is connected to pin 1 on the other end, pin 2 on one end of the cable is connected to pin 2 on the other end, and so forth. In this case, the pins are connected see Figure 1 and Figure 2. A convenient rule of thumb is to use a crossover cable when the two ports that are connected are in the same layer of the OSI model. If you cross OSI layers, use a straight-through cable.

Some devices, especially common on hubs, have a button that can toggle between accepting a straight-through or crossover cable. Therefore, this rule of thumb does not always apply.

Note: Use a crossover cable when you connect two ports in the same layer of the OSI model, such as router to router Layer 3 or switch to switch Layer 2. Use a straight-through cable if the two ports are in different layers, such as router to switch Layer 3 to 2 or PC to switch Layer 3 to 2.

For this rule, treat a PC as a Layer 3 device. Activate an internal crossover function and this type of port allows the device to connect to an Ethernet port on a switch that uses a straight-through patch cable. Turn the MDI switch on to perform this. When the MDI switch is in the out position, the port expects to be connected to an end-user device.

If you use an Ethernet port on the switch with a fiber interface to connect to another switch port, a router port, or other Layer 2 device, you need to reverse the connection on one of the devices. Rotate the connector one half turn or cross over the individual fiber connectors to reverse the connection. Think about each fiber as either fiber A or fiber B. Automatic medium-dependent interface crossover Auto-MDIX is a feature that allows the switch interface to detect the required cable connection type straight-through or crossover and automatically configure the connection appropriately.

With Auto-MDIX enabled, you can use either a straight-through or crossover type cable to connect to the other device, and the interface automatically corrects for any incorrect cabling.

Cisco recommends that auto-negotiation be used when the devices involved are compliant with the Auto-negotiation is very useful for ports where devices with different capabilities are connected and disconnected on a regular basis. A good example is offices that are used by visiting employees who bring their own laptops. This resets both the speed and duplex mode to auto-negotiate. Look for the a prefix in the status fields. This indicates the port is configured for auto-negotiation.

Examples are a-full and a If the a prefix is not present, the port is manually configured for the parameters shown.

Examples are full and You receive this error because you need to manually configure the speed on a port before you can manually configure the duplex mode. Why does a port not detect the correct duplex mode when the link partner is not configured for auto-negotiation?

Why is it possible to have link show connected when the two ports have different duplex modes configured? It is possible because the electrical signals the ports use to determine if they are connected do not track the status of the duplex modes. Does the a prefix on the duplex and speed status fields always mean the port has auto-negotiated behavior?

This means the CDP determines, via a configuration comparison dialogue, that a mismatch exists. CDP does not attempt to resolve the mismatch. Skip to content Skip to search Skip to footer. Available Languages. Download Options. Updated: July 15, Contents Introduction. Was this Document Helpful? However, cabling gets damaged, configurations change, and new devices are connected to the switch that require switch configuration changes.

Ongoing maintenance and troubleshooting of the network infrastructure is required. To troubleshoot these issues when you have no connection or a bad connection between a switch and another device, follow this general process, as shown in Figure , and explained thereafter. Figure Troubleshooting Switch Media Issues. I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.

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