Cisco Router and IOS How To’s

Welcome to CellStream’s Cisco Router and IOS How-To Resource Center. This collection of articles, configuration examples, troubleshooting guides, and practical tutorials is designed to help network engineers, technicians, students, and IT professionals better understand, deploy, manage, and troubleshoot Cisco networking equipment.

Whether you’re learning the fundamentals of Cisco IOS, configuring routing protocols, implementing security features, troubleshooting connectivity issues, or preparing for certification exams, you’ll find practical, real-world guidance based on industry experience and proven best practices.

The content provided here is intended to help simplify complex networking concepts and provide actionable solutions you can apply in your own environment. As with any network configuration, always validate commands and procedures in a test environment before implementing changes in production networks.

We welcome your feedback and suggestions. If you have questions about any of the content, ideas for additional topics, or requests for Cisco technologies and configurations not currently covered, please contact us using our Contact Us form. Your input helps us continue expanding and improving this resource for the networking community.

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Maintenance with the ‘show diag’ command in Cisco IOS

Cisco Router and IOS How To's / By

Post Views: 1,942 Routine maintenance is the underpinning of any well run network. Through routine maintenance, consistency, predictability and standardization all result allowing the network to operate as expected and in times of fault, makes a better troubleshooting environment. As part of any routine maintenance activity, Cisco provides several commands to help. One less known […]

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Leveraging Logging for Troubleshooting Using Cisco IOS

Cisco Router and IOS How To's / By

Post Views: 4,489 Whenever we teach our Hands-On courses, we always have a section of the course that discusses troubleshooting the network or technology the class is learning. A key part of troubleshooting any network is knowing the technology, no argument. But even the masters of technologies like Multicasting, or IP Networking, or MPLS, still

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Service Timestamps in Logging in Cisco IOS

Cisco Router and IOS How To's / By

Post Views: 4,381 You can use the service timestamps command to create timestamps on the router’s log files. Since version 11.3, the Cisco IOS has enabled certain timestamps by default, so most of us have this on. However, there are additional timestamps options that you can enable as well as places where timestamps are probably

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Stopping and Changing the –More– Console Output Interrupt

Cisco Router and IOS How To's / By

Post Views: 1,554 One of the most annoying things in Cisco IOS is its old roots in the 23 line terminals.  Every 23 lines, you get a –More– pause, to which you have to hit the space bar to continue the output. Now maybe this does not bother you.  Fine, move on to our next

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Keeping VPN SA’s Refreshed in Cisco IOS

Cisco Router and IOS How To's / By

Post Views: 1,182 Many people are using VPN technology today to ensure data confidentiality between remote locations. When using a site-to-site type VPN (say between a Router and a Firewall), a common complaint among end users is intermittent delay before VPN traffic is successful. This is usually due to Security Associations (SA) becoming too old

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Spanning Tree Protocol Configuration Basics in Cisco IOS

Cisco Router and IOS How To's / By

Post Views: 1,514 As many of our students and clients have learned, Spanning Tree in Layer 2 Ethernets is a basic control protocol that removes logical loops from physically looped networks creating the Spanning Tree. This How To focuses on the essential configuration commands in Cisco IOS that you need to know to manage Spanning

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IP Spoofing Security Tip in Cisco IOS

Cisco Router and IOS How To's / By

Post Views: 2,207 All router administrators need to take whatever security precautions they can to prevent attacks to their systems and networks. While these attacks are a continually moving target, a common attack to IP networks is called IP Spoofing. This is accomplished by sending IP packets into the network with source addresses that appear

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Cisco IOS Order of Operations for NAT and QoS

Cisco Router and IOS How To's / By

Post Views: 2,658 When learning Cisco IOS, students often ask, what happens if there is conflicting information? Cisco IOS order of operations plays an important role in how a router processes traffic and makes choices, especially if there are two possible answers. If you’re simply using the most basic features of the router, chances are

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HSRP – A Quick Configuration in Cisco IOS

Cisco Router and IOS How To's / By

Post Views: 1,725 The following is a quick example on how to configure Cisco’s HSRP protocol. Many net admins ask about redundancy in Cisco routers and the answer is usually always the same: If your uptime has to be high, and the thought of having a failure and suffering the downtime that it will take

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Finding Configuration Details Quickly in Cisco IOS

Cisco Router and IOS How To's / By

Post Views: 1,460 Finding the right piece of information that you need from a Cisco router can often be a challenge. For example, if you use the show running-config command on a large production router, you can end up with 25 pages of text output. Locating that one piece of information you’re looking for can

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File Commands and their Usage in Cisco IOS

Cisco Router and IOS How To's / By

Post Views: 17,942 Similar to a Windows or Linux operating systems that have a command line or terminal commands to manipulate files, the Cisco IOS (though rooted in Unix) and has its own list of commands to manipulate files. These commands are very similar to DOS/Windows commands. Files could be your IOS router operating system

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Configuring EtherChannel on Cisco Switches

Cisco Router and IOS How To's / By

Post Views: 1,432 What is EtherChannel? EtherChannel technology is another way for you to increase the bandwidth of your core network links and provide redundancy of LAN links. It allows you to achieve greater speed by bundling Fast Ethernet or Gigabit Ethernet links, which makes a switch or router use the merged ports as a

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CONFIG_RESOLVE_FAILURE error Quick Fix in Cisco IOS

Cisco Router and IOS How To's / By

Post Views: 3,342 In this article, I will explain steps to correct a CONFIG_RESOLVE_FAILURE error in Cisco IOS. \If you are like many users of the latest IOS, you may find your routers constantly outputting a message like this: cell_pe1# %Error opening tftp://255.255.255.255/cisconet.cfg (Timed out) 19:20:43: %SYS-4-CONFIG_RESOLVE_FAILURE: System config parse from (tftp://255.255.255.255/cisconet.cfg) failed The reason

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