Each networking device can be configured in different ways. Most types of misconfigurations generate problems within the network, including:
- Poor throughput
- Lack of connectivity
A device can be connected to the network, have a signal, and be able to communicate to the Internet and to other devices but the performance might be low, in a consistent and easily reproducible way. This can manifest during normal operations, including file transfer or other types of communications with the rest of the network.
With major configuration issues, the issue might manifest as complete lack of connectivity, including no link lights on the specific device ports. Sometimes the link lights are on but you still lack any kind of connectivity. This shows that the signal is passing through the cable, which means that you don’t have a cabling issue but rather a port configuration issue on one port or the other. This requires problem investigation in the device’s configuration.
There are a number of different settings when configuring a port, including:
- Speed
- Duplex
- Encapsulation/VLAN.
Most of these parameters have to be synchronised on both sides of the link, either by manually configuring them or by enabling port autoconfiguration. If detected, this method will send negotiation packets on the link to each device to detect the capabilities on the other end device and commonly agree on the best possible parameters supported by both of them to ensure an optimal transmission. The problem is that sometimes autoconfiguration does not select the best parameters for your needs, so you should also verify this and manually configure the ports according to each specific case.
If you are performing manual configuration on each port, one of the first parameters you have to take care of is the interface speed. This has to be identical on both sides of a link. If you configure it incorrectly on one side, the link might not be operational. Another related setting is port duplex, which can be configured to be either half duplex or full duplex. You can configure a link with half duplex on one side and full duplex on the other side, and even though the link will come up, the throughput will be highly affected because each side is expecting to handle communication in a different way. This will result in collisions which will affect the transmission on that particular link. Make sure that both sides use the same duplex settings in order for the traffic to be sent as efficiently as possible.
If you are operating in an enterprise-level environment, you might need to use different VLANs to segment the traffic. Each switch must be properly configured in this regard so each switch port is assigned to the correct VLAN. If you are directly connecting ports configured to use different VLAN IDs, the communication will be broken at Layer 2, even though the Physical Layer shows no issues.
By examining all the port configuration options presented above and making sure that you have everything synchronised at both ends of a link, you can be assured that the connectivity and throughput of the configured devices will be optimised.