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Cisco Network Troubleshooting for Beginners

Cisco Network Troubleshooting for Beginners

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In your role as a Network Engineer your primary responsibility is to make sure your network equipment functions in a safe and efficient manner in all instances. However, we all know that every device could fail. The reason for this may be due to software issues or hardware issues, or even environmental dangers.

When you encounter such unpredictability it is your job to pinpoint and determine the source of the issue and rectify it as fast as you are able to. This is why it’s useful to be aware of specific strategies which have proven to be vital and crucial in the realm of networking.

In this article, I’ll discuss the most crucial commands you’ll definitely find useful and possibly even necessary during your career in networking and especially during troubleshooting issues. The commands I’m talking about, and that are extremely valuable are:

Ping

Traceroute

Telnet

Interfaces to show

Start-up-config to show

The Ping Utility

The PING command works via the Network layer and utilizes the functions that are provided by the ICMP protocol. It is the very first command you must start your troubleshooting procedure.

By using PING, you can check whether an external host is still alive by transmitting echo requests and receiving echo responses from the host.

I’ve talked about PING extensively in my previous posts. For more information on PING look up How to Troubleshoot Your Connections using Ping as well as Traceroute.

The PING command offers quite many choices from which you could profit. For instance, you could select to use various network protocols. Furthermore, you can specify the precise amount of PING requests that will be sent. Buy refurbished dell emc products uae at low price.

Additionally, you can select the length of the data in the echo request packet (provided as bytes) and specify whether fragmentation of the packet is permitted or not permitted during transmission. The two last options of collaboration can be utilized to determine the lowest MTU that is available within the communication route.

On Cisco devices, the easiest method of using the utility PING is to send the command PING and your IP address.

Network Troubleshooting 1

To access more advanced features, simply type in PING and follow the prompts from then from:

Network Troubleshooting 2

The Traceroute Command

The TRACEROUTE command tracks the complete path it takes through an internet network. Similar to PING it utilizes the ICMP protocol and TTL timeouts for its task.

For more information about this command, check out How to Troubleshoot Your Connections using Ping as well as Traceroute.

This command is extremely useful to identify potential bottlenecks in the transmission route. Here is an example output from the TRACEROUTE command

Network Troubleshooting 3

The Telnet Command

Utilize the command telnet to test the TCP stack and software that is used to connect the source and destination stations. Of course, in order to be able to connect via telnet on the Cisco device, the device must be configured to allow connection via telnet. To make use of TELNET simply issue the telnet command , along with the hostname or IP address for the station remote.

Network Troubleshooting 4

The Show Interfaces Command

Show interfaces lists all available interfaces which can be set up in the Cisco device. It is possible to explicitly make use of this command to display only the details of a particular interface by putting the interface’s name following that shows interfaces commands. 

This command is highly efficient as it can uncover layers 1 and 2 issues. Additionally, this command gives information about what is the physical address (MAC) as well as the IP address, encapsulation technique and data regarding incorrect conditions on the particular interface. Check the output of show interface for fastethernet:

Network Troubleshooting 5

In the first part of the command show interface is the most significant one. The first parameter is referring to the physical layer.

In this instance FastEthernet 0 is up and in this case, FastEthernet 0 is operating. The second portion of the line is the Data Link Layer. Data Link Layer; therefore the line protocol is in use. This means we are connected to layer 2 also. There are four outputs you could see:

FastEthernet0 has been launched, the line protocol is also up. Both the physical and Data Link layers on the interface are working properly.

FastEthernet0 has stopped working, line protocol has stopped: The message is a sign of a physical interface issue. For instance the cable connected to this interface or the remote interface has been disconnected.

FastEthernet0 is running, but the line protocol has gone down. In this situation, the Physical layer is in operation. The line protocol’s failure suggests a framing or clocking issue. Possible causes are encapsulation , and clock rate inconsistencies. Buy refurbished dell r810 specs price online in India.

Ethernet0 is currently down administratively the line protocol is not working This output means that a local network is shut down by hand by using the command shutdown.

The Show IP Interface Command

The show ip-interface command will provide information regarding layer 3 configurations on interfaces. With this command, you will be able to determine the IP address and mask that is configured for a particular interface, as well as whether an access list is in place to the interface and also the basic

Information about IP.

Network Troubleshooting 6

The Show IP Route Command

Utilize the show ip route command to obtain specific information about the routes that are configured by the router. Be aware that the router is able to connect to the networks that are listed on its route table. 

It’s possible that the router will not connect to a network that you have manually set up, and the route you specified is deleted from its table and this is the reason why you need to make use of this command along with show ip route in order to detect any inconsistencies.

 

For more information about IP routing issues, read my article on default and static Routing Basics.

Network Troubleshooting 7

Show Running-Config and Show Startup-Config Commands

Use the command showrunning to determine the entire configuration that your Cisco devices run on. Through examining the particulars of your device, the configuration can help you determine the root of your issue. 

Utilize this command in order to view the configuration commands which will be loaded on your device when it restarts. Compare it with the current configuration to find any possible irregularities.

Network Troubleshooting 8

In the End … Follow Your Instincts

The process of identifying a malfunction in a network isn’t an easy job. In many instances, you’ll have to dive into deep water to pinpoint the issue. That means you’ll likely have to go through all the bytes and bits to find the error.

Many tools for monitoring networks can assist you in these challenging tasks. While there’s plenty you can do, you need not to lose faith, be patient and go with your instincts.

Sometimes, the issue you’re looking for is directly in front of your face and then slips from your grasp, right when you think you’ve got it. Be persistent Be patient, and keep in mind you’ll take the fight to victory!

Prepare yourself; to win and effectively, you need to be equipped with the right equipment. Therefore, you should know your device well and understand how it works and how to apply the fundamental troubleshooting commands you’ve learned to be able to determine the issue or at a minimum, determine the source of the issue. Have fun!

 

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