What are the top troubleshooting tips for networking issues?

During many years in TAC, I have found one thing very useful time and again and that never skip basics. Keep the OSI layer in mind. For example, if ARP for next hop is not resolved, layer 3 traffic would of course be affected. Refer the resources at your disposal like documentation, configuration guide etc. It is very important to understand relationship between control plane and forwarding plane. This will help isolate issue to specific device or segment. Ask the right questions. Understanding complete traffic vs partial traffic drop, drop vs latency is crucial as they can take different course of troubleshooting. Never assume and never jump to conclusions before required information is collected and analysed.

I am a great fan of the OSI 7-layer model. Use this model to focus your thoughts and determine at which layer(s) the problem is occurring. The very first thing to do is have a clear and concise description of what the fault is and then verify that the problem is still a problem. Work the 7 layer model to eliminate the problem. If there is not an obvious layer to start, I suggest starting at layer 3 and then work up or down as appropriate. Some faults are at layer 8!

If you've followed all the advice above but are still having trouble you can try: - telnet on needed ports to see if the communication is alowed from source to destination. - while doing telnet capture tcpdump so that you can inspect idf the packets are ariving and if they have some errors. - ask if the problem is intermittent or constant. If it always shows up at the same time of the week (perahps there is backup process consuming all the bandwidth) or at the same time of the day (peak network utilisation). - does the probelm affect just traffic to specific destination or only from specific source. - foes the traffic work when you are targeting ip addrss but not when you are targeting fqdn (suggesting dns issue).

Always starts with fundamentals, like reachability using ping/ traceroutes, at times due to restrictions/limitations pings would be blocked, in that cases traceroutes should help. L2 [ STP/ PO] L3 [ ARP/ control plane/data plane verification], Physical layer isolation. Do not assume, ask a lot of open-ended questions until you understand the end-to-end issue. One thing I have always observed for any major incidents/ issues, solutions are very basic and simple. If we skip the fundamental networking questions, then we might end up breaking up a lot of things, and time-consuming.

Traceroute is the best tools for me, this is the first tool used to check my network problem. You can use this tools to check the troubling path on your network, so you can know where to fix the problem.

some key troubleshooting tips for networking issues: - Check Physical Connections - Verify Network Configuration - Restart Network Devices - Test Connectivity - Check Firewall and Security Settings - Review Network Logs - Test Different Network Components - Update Firmware and Drivers - Use Network Monitoring Tools - Consult Documentation and Online Resources

some additional troubleshooting tips for networking issues: - Check the physical connections - Restart your devices. - Update your drivers and firmware - Run a virus scan - Disable your firewall and antivirus software temporarily - Check your DNS settings. DNS stands for Domain Name System - Contact your ISP If you are starting a career in computer networking, it is important to learn how to troubleshoot network issues. By following the tips above, you can be well on your way to resolving even the most challenging problems.

The troubleshooter tool is good, but sometimes you still need to fix the problem manually. - Check dns response, if you cant resolve make sure the dns configuration on your device. - Use Traceroute and Ping tools. - Check your device time.

Here are some additional tips that might help: - Restart your devices: Computers, modem and router. - Disable/Re-enable Network Adapter: In Windows, you can disable and re-enable your network adapter in the Network and Sharing Center. -Check firewall and Antivirus settings: Sometimes your security software can block netowrk traffic. -Run Network Troubleshooters: Both Windows and macOS have built-in network troubleshooters that can help identify and fix common issues - Check for malware: Run a malware scan to ensure that your system is not infected, as malware can disrupt network connectivity

Always record the initial settings of anything you change! If you changing of settings does not fix the problem, put everything back to how you found it. If you change multiple things and the problem resolves, determine which setting change(s) fixed the problem and put all the other settings back to the original settings. If you don't do this, you may introduce new problems now or at a later date. Update any documentation that needs it to reflect the new configuration, with a note as to why the change has been made.

Yes, networking issues could be fixed by a simple configuration change as that of a duplex mode setting of the networking interfaces of the connected devices. So watch for duplex mismatch (half or full) settings on interfaces

Always provide relevant logs in advance to support team, it will save alot of time. For example if you are reporting a network related issue for a RHEL server then always provide sosreport and outputs of ip command specific to the interface you are facing issues with.

My 'Starter for 10'. - Study how to troubleshoot. - Keep a log of what you do & when. This allows you to: - Undo things that you have done if needed. - You have the details for the report you may need to write. - If another fault occurs while you are trouble shooting, you can show what you did and when. This may help fix the second fault that occurred. - Get a manager or PM to run interference for you while you are fixing the problem. Keep them informed of what you are doing at a high level and they can update people that come to see you about what progress is being made & you can keep your focus on fixing the problem. - Fixing the problem is not the end of it. You need to find 'Root Cause'. A new device driver on a PC for instance

- Reverse engineering the network and understand the overall picture should be key, that gives you an idea about the individual pieces that made the network functional in the first place. i.e. What protocols, services, applications...etc makes the network. - Follow bottom to up approach - It doesn't matter if BGP, OSPF, DNS, STP...etc are properly tuned and working fine if the fiber is broken or the SFP is defective. So we should always start from the bottom layer as that is the layer all upper layer protocols depend.