How can you troubleshoot network connectivity issues using common devices?

1 Check the physical layer

The first step in troubleshooting network connectivity issues is to check the physical layer, which includes the cables, connectors, and ports that link the devices on the network. You should inspect the cables for any damage, looseness, or mismatching. You should also make sure that the devices are powered on and have the correct LED indicators. If you suspect a faulty cable, connector, or port, you can try to replace it or use a different one. You can also use a cable tester to verify the integrity of the cables.

2 Check the network layer

The second step in troubleshooting network connectivity issues is to check the network layer, which includes the IP addresses, subnet masks, gateways, and routing protocols that enable the devices to communicate on the network. You should verify that the devices have valid and unique IP addresses and subnet masks, and that they are in the same network segment or can reach each other through a gateway or router. You can use the ping command to test the connectivity between two devices by sending and receiving packets. You can also use the traceroute command to trace the path and hops that a packet takes from one device to another.

3 Check the transport layer

The third step in troubleshooting network connectivity issues is to check the transport layer, which includes the TCP and UDP ports that enable the devices to establish sessions and exchange data on the network. You should verify that the devices are using the correct ports and protocols for the applications or services that they are running or accessing. You should also check the firewall settings and rules that may block or allow certain ports and protocols. You can use the netstat command to display the active connections and listening ports on a device. You can also use the telnet command to test the connectivity to a specific port on a remote device.

4 Check the application layer

The fourth step in troubleshooting network connectivity issues is to check the application layer, which includes the software and programs that provide the functionality and user interface for the network users. You should verify that the devices have the latest updates and patches for the applications or services that they are using or providing. You should also check the configuration and settings of the applications or services to ensure that they are compatible and consistent with the network requirements. You can use the nslookup command to query the domain name system (DNS) server for the IP address or hostname of a device. You can also use the curl command to send and receive data from a web server.

5 Use network monitoring tools

The fifth step in troubleshooting network connectivity issues is to use network monitoring tools, which are software or hardware devices that can analyze and report the status and performance of the network. You can use network monitoring tools to collect and display information such as bandwidth usage, packet loss, latency, jitter, errors, and alarms. You can also use network monitoring tools to generate and simulate network traffic and conditions to test and verify the network functionality and reliability. Some examples of network monitoring tools are Wireshark, Nmap, iperf, and SNMP.

6 Consult network documentation

The sixth and final step in troubleshooting network connectivity issues is to consult network documentation, which are the records and diagrams that describe the network design, architecture, and configuration. You can use network documentation to understand the network topology and devices, the network policies and procedures, and the network troubleshooting and recovery plans. You can also use network documentation to compare and contrast the current network state with the expected or desired network state. Network documentation can help you identify and isolate the root cause of the network problem and find the best solution.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?