The following article is intended to provide troubleshooting tips for core networks where 1 router and 1 or more switches are used for communication. I provide industry best practices, as well as my own experience and experience.
Main network components:
ISP broadband modem
WAN and LAN Router
DHCP server
Ethernet switch
Devices (computers, servers, phone printers, etc.)
Short description:
ISP Modem: Is your device provided by an Internet Service Provider (ISP) device that allows you to connect to your communication lines to access the Internet. Usually cable providers do the wiring and install a cable modem according to your promises. For services such as DSL, you may have to provide a modem yourself. Another option is Smart Jack, which your provider installs in Dmarc using T1 lines.
Router: A router is a device that directs traffic to the appropriate destination. Usually for a small business device, a router performs other functions, such as DHCP, firewall, WebContect filtering, etc. For the purpose of this article, we will not use routers that perform their basic routing function and DHCP service.
Ethernet switch: or just a switch, this device connects network devices.
Devices: everything that connects to the network.
Handle:
Step 1. Make sure the problem really exists.
Make sure the problem is real and not the problem of the user or the application. I’ve seen it countless times when a user complains about a network doesn’t work, and it’s simple, as simple as a user never presses the send button to send email.
Step 2. Identify the problem.
This is a problem of communicating with only one device, it happens only with a few users, does it happen with everyone in the company?
Step 3. Isolate the problem.
Once you have identified the problem, concentrate on the affected area. For example, if only one user with network problems starts troubleshooting at the local level, before moving on to other areas.
Step 4. Troubleshooting: use the following basic functions:
1st level
• Make sure the network connection is turned on.
• Make sure the network cable is connected (if the user connects over a wireless network, make sure the user is connected to the correct network). When connected to the network, the LED of the Ethernet card flashes.
• Make sure the device is connected to a network switch (you usually see a flashing LED on the port connected to your device).
• Check if the Ethernet cable works; the cables do not work well for many reasons.
• Connect the device to the working switch port.
Level 2.
• Make sure the Ethernet card is configured with an IP address. For windows you can use the ipconfig command, for linux you can use ifconfig. If your IP address starts at 169.254, the device cannot reach the DHCP server.
• If you have a valid IP address (similar to other devices in the same area), try checking your default gateway. If he answers successfully and this device is the only one who cannot connect, you may have to check the routing table to make sure everything is fine. I saw how this happens as a result of the virus and how normal the work is. For Windows computers, you can use the arp -a command to view the arp table.
• After you have confirmed the above and still not connected, you can deal with a bad Ethernet card. Yes, Ethernet cards do not work well.
Level 3
• I leave it for another article, but you can start looking for router settings, DHCP, firewall rules, DNS, etc.
The key to successful troubleshooting is "maintaining a systematic layering process" and "Documenting your results." These recommendations are not written in stone, but are an important part of the troubleshooting process. Good luck in troubleshooting the network!
