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 […]
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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
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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
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OSPF (Open Shortest Path First) is an IGP (internal gateway protocol), and OSPF is an open standard protocol originally defined in RFC 2328. Since then OSPF has been updated numerous times including functionality to support IPv6 and Address Families. OSPF is supported on every major routing platform as well as Windows Server 2003 and Linux
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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.
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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
Maintenance with the ‘show diag’ command in Cisco IOS Read More »
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
Leveraging Logging for Troubleshooting Using Cisco IOS Read More »
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 requiring a ‘VPN
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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 Cisco tip. But
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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 Tree. Important note:
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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 to be part
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IP mobility is software and hardware designed to provide network access as a user travels from network to network. Cisco calls this the ubiquitous connection. Cellular telephone networks already accomplish this: You can begin a cellular call in Los Angeles, CA and (in theory) you should be able to drive to New York city without
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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 to make the
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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 good that you’ll
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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 take a lot
Finding Configuration Details Quickly in Cisco IOS Read More »