One of the most frequent IT-related issues we encounter deals with connectivity. “I can’t get to the Web,” “The Internet is down,” and “It doesn’t work” are far more complicated than you think.

In general, networking issues fall into one of four categories:

1. Problem with the computer network interface
2. Problem with the local network
3. Problem between the local network and the rest of the web
4. Problem with the target resource. (website, server, application)

Research network troubleshooting as it relates to each of these categories of problems and how they may be resolved.

Create a flowchart that illustrates how to navigate the troubleshooting process to most effectively solve the problems.

Be sure to cite your research using APA guidelines found in the APA Style Guide, located in the Student Success Center.

Basic Network Troubleshooting Steps and Tools

An Extensive Study of Network Troubleshooting with the Tools used.

We explored all about Network Security along with its types in our previous tutorial.

When we run a network or while working in any system there are always chances of failure in the smooth operation owing to technical, physical or any other faults.

For uninterrupted running of the system, we need to resolve the raised issues as soon as possible and for this, we need to detect the cause of the problem first and then fix it.

Must Read => Beginner’s Guide to Networking

Thus the process of detection, minimization and resolving the faults that arise in the network while performing the various day to day activities is known as troubleshooting.

Here we will explore the different kinds of troubleshooting steps and the tools we use for fault detection and closure of the same.

NETWORK TROUBLESHOOTING

What You Will Learn: [show]
Network Troubleshooting

In this tutorial, we are only concerned about the computer networking fault diagnosis and rectification.

Based on the type of issue, we will discuss its troubleshooting steps and tips.
Basic Network Problems

Cable Problem: The cable which is used to connect two devices can get faulty, shortened or can be physically damaged.
Connectivity Problem: The port or interface on which the device is connected or configured can be physically down or faulty due to which the source host will not be able to communicate with the destination host.
Configuration Issue: Due to a wrong configuration, looping the IP, routing problem and other configuration issues, network fault may arise and the services will get affected.
Software Issue: Owing to software compatibility issues and version mismatch, the transmission of IP data packets between the source and destination is interrupted.
Traffic overload: If the link is over utilized then the capacity or traffic on a device is more than the carrying capacity of it and due to overload condition the device will start behaving abnormally.
Network IP issue: Due to improper configuration of IP addresses and subnet mask and routing IP to the next hop, the source will not be able to reach the destination IP through the network.

Network Troubleshooting 101

Network Troubleshooting Flowchart

Network troubleshooting-flowchart

[image source]
Steps Involved in Network Diagnostics

Here steps to troubleshoot and diagnose various network problems like IP, connectivity, wireless connection, etc.
Troubleshooting IP Problems

In the TCP/IP protocol suite, if we are not able to reach at the destination IP address and not able to find the route to reach the next hop at any point in the network, then we will use PING and TRACEROUTE tools for troubleshooting the cause and location of the issue.

The generic steps to troubleshoot the IP related issues in the network include:

Firstly locate the pair of devices between the source and the destination host between which the connectivity issue has occurred.
Once you locate the devices using the tools, the fault can be due to a physical connectivity issue. Thus check the physical connections all over the path.
There can be a fault in the LAN connectivity as well if you are working in a LAN network. So check the LAN connections. The local port can be faulty or down due to which the source cannot be able to reach the destination IP.
One of the reasons of the fault can be the router connectivity issue while traveling through various paths to reach the destination. Hence check that if the router is defined properly at each of the intermediate hops.
Check the configuration settings.

Troubleshooting Local Connectivity Issues

Once on the broad level, if you find that there is an issue in the LAN connectivity, then in order to locate the root cause and to resolve it, you should follow the below steps:

If the destination and the source are of the identical subnet mask, then try to ping the destination IP.
Else, if the destination is of some other subnet mask then try to ping the gateway IP address of the router.
Now, if both the ping fails, then first check that in the configuration settings, if both the subnet mask and route to be followed to reach the destination are defined properly in the routing table or not?
Once you are done with the configuration part and found everything OK, then check if your source host is able to ping some another hop in the LAN network other than the destination host or route to that?
If you are not able to ping to another device then there can be many reasons for this. It may even be a configuration issue, a physical connectivity issue, and repetitive IP address entry issue.

Correcting the Repetitive IP address Entry Issue

For rectifying the duplicate entry of an IP issue, disconnect the doubtful device from the LAN and also make the interface on which the device was connected shut down.

Now ping the device from some another device of the same subnet or LAN network. If the ping is OK, then it indicates that the IP is being used by some other device as well on the network. From the ARP table of the device, find out its MAC address and modify the IP address according to planning.

But if the problem persists still, then there will be a physical connectivity or configuration issue in it.
Troubleshooting Physical Connectivity Issues

The list of faults that come under this category are:

Improper connection of cables
Router, switch or hub port is faulty or down.
Traffic overload on the link or particular interface.
Configuration issue at layer-1.

Let’s take a look at the above in detail.

#1) Checking Cable connectivity Issue: The cables are used for connections, based on the type of connectivity. Like, for connectivity between a router and a computer the crossover pair of the cable is used. Thus make sure that the suggested and suitable cable is used to make a physical connection between any two devices.

If connections are found ok, then maybe the cable is faulty, so check the connectivity by replacing the existing cable with a newer one. Still, if the problem persists, then check the port or interface on which the link is terminated. There is a possibility for the port to be faulty.

Network Troubleshooting 101

#2) Port Faulty Scenario: Check that the port or interface on which the link is established is not shut down. Verify the duplex mode and speed as well. If the port is up and still the problem persists, then there are indicator lights that are present on each of the device to show the running status of the port.

From the indicator lights, check if the port is physically radiating or down. If the port is physically malfunctioning then it will appear by light status. In this situation, configure the link on some other free port or interface.

#3) Traffic overload: If there is more traffic than the carrying capacity at a link or interface then at some point it will start behaving abnormally. Thus verify these criteria to ensure smooth running.

#4) Configuration Issue: Check the router configuration on the interface by show ip interface and show running-config commands.
Troubleshooting Routing Problems

When we route the data packets in the network, then the chances for occurrences of fault are usual. Thus depending on the type of fault, we will prepare our plan for resolving the faults.

The kind of fault that occurs between the source and destination hosts while floating data packets in a network are listed below:

The route is not defined in the router between the source and destination.
A wrong Routing protocol is used to find out the route to the next hop or destination.
Software related fault at the router.
Any filter or firewall may be barring the entry of data packets to the destination node.
There may be configuration faults that arise at the source router end.

Network Troubleshooting 101

How to proceed for resolution:

To find out the resolution, the first step is to locate the hop between the source and the destination where the problem has occurred.
The process verifies the IP connectivity and routing protocols connectivity at each hop starting from the source host towards the destination one.
We can also use the traceroute tool to locate the hop where the problem has arised. But this is not helpful in all the cases. Hence, it is better if we proceed with the first one.
Once we locate the problematic hop, then login to that router via telnet and then try to ping the source and destination host.
If the ping is not successful, then verify the routing table for routes between the source and destination. If routes are not defined then configure the IP routes with the subnet mask and default route in the router.
In condition, if the ping responses with only a few percentages of success, then there may be multiple paths that are defined to reach the destination. But out of multiple paths, one is failing to reach the destination. The cause for this is that a routing loop can occur in the path. To rectify this, trace the looping hop, and correct the configuration.
After rectification of the above steps, if still, the problem persists, then check the routing protocol used, and change the protocol in accordance with the network.
The configuration issues at a particular router can be checked using a command like show ip interface for interface related faults, show ip access-group for finding out ant firewall or filter is configured in the network and you can check what is allowed to pass through it, show version for uptime and show running-config for the overall configuration….

ORDER NOW FOR AN ORIGINAL PAPER!!! Network Troubleshooting 101

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