Author name: Andrew Walding

As most of us know, a key to managing the Internet is knowledge of TCP and UDP port numbers. Cisco IOS uses Access Control Lists for many purposes, but in this tip, we will focus on TCP and UDP port numbers. Port numbers are unique, well-known, registered or ephemeral numbers used by TCP (Transmission Control […]

Network broadcasts can create a huge amount of traffic on your organization’s network. When one device sends out a single broadcast, that broadcast goes to all devices on the subnet or VLAN. How can you manage these broadcasts to make your network more efficient? One method is to use Cisco Catalyst broadcast suppression — also

Welcome to our Cisco IOS Classic Interface Commands Cheat Sheet. You can see our other IOS cheat sheet here.  You can view all our Cisco IOS How To’s here. Here are the most frequently used Interface commands as a quick reference/cheat sheet. This will help you remember the key interface configurations: Important show commands show

The Show Environment command can be very helpful to alert you of potential hardware issues. You will need to access this command in global Exec mode. Here are the options available for the Show Environment command: show environment [alarms | all | fans | hardware | last | leds | power-supply | table | temperature

The primary purpose of the show interfaces command is for displaying the equipped interfaces and their status. Here’s the information you can get about an interface from this command: Interface type Status Speed and duplex Encapsulation Errors on the interface The last time the interface flapped The last time the error counters were reset Utilization

What happens if there is a system or user on a VLAN that is infected by malware or is deliberately running a scanning program? What if you have some public ports on your switches that you only want to have access to the Internet and not each other? This problem can be easily solved with

Point-to-Point (PPP) Protocol is an excelent Layer 2 protocol used to establish a direct connection between two nodes. It can provide connection authentication, transmission encryption (using ECP, RFC 1968), and compression. PPP was designed somewhat after the original HDLC specifications. The designers of PPP included many additional features that had been seen only in proprietary

What is Policy-based Routing? With policy-based routing (which we will call PBR from here on out), you get the option to implement policies that selectively cause packets to take different paths. Additionally, PBR can mark packets so that certain types of traffic get prioritized. One example of PBR is, say that your OSPF routing protocol

This How To explains Passwords on Cisco platforms. The question you might ask is: Doesn’t the router already have default passwords? The answer is NO, it doesn’t. There is no automatic password defense that comes with your router. As a Cisco admin, this should be taken very seriously. It is so important and so easy

If you want to partition flash memory of routers with flash, you can.  On most class B Flash file systems, you can partition banks of Flash memory into separate, logical devices so that the router can hold and maintain two or more different software images. This partitioning allows you to write software into Flash memory

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 can benefit from

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 off by default.

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 command is the