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 […]
Keeping VPN SA’s Refreshed in Cisco IOS Read More »
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:
Spanning Tree Protocol Configuration Basics in Cisco IOS Read More »
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
IP Mobility Primer in Cisco IOS Read More »
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
Cisco IOS Order of Operations for NAT and QoS Read More »
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
HSRP – A Quick Configuration in Cisco IOS Read More »
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 »
Similar to a Windows or Linux operating systems, the Cisco IOS is 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 executable, configuration file(s), or other type of IOS file. Knowing these file commands is
File Commands and their Usage in Cisco IOS Read More »
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 single port. This
Configuring EtherChannel on Cisco Switches Read More »
No one wants it to happen but, sooner or later, you will experience a router crash. When you do, you will want to be prepared to save that critical router memory information in order to find out why the router crashed and prevent future crashes. To do this, you need to configure your router to
Core Dump in Cisco IOS Read More »
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 for this message
CONFIG_RESOLVE_FAILURE error Quick Fix in Cisco IOS Read More »
Anyone who has network admin access can make changes to the running configuration on a router or switch at any time. If you are running a large IT shop or in charge of just a few folks, this feature will enable you to control the concurrent changes to your running configuration. Exclusive Configuration Change Access,
Configuration Lock in Cisco IOS Read More »
Sometimes, we need to transfer IOS from one router/platform to another. Other times, we can end up in Rommon> prompt because an IOS download failed of similar issue. Let’s start with a stranded router. It is strongly suggested that you get a PCMCIA memory card, insert it into a good router. From priviledged mode on
Copying Cisco IOS from One Router to Another Read More »
This How To discusses how to set up one Cisco Router as a PKI Server and one Cisco Router as a client. That’s right, you can set up a Cisco router as a Certificate Authority (CA) and then set up other routers as clients to use that CA to authenticate on your network. The advantage
PKI Server and Client Setup in Cisco IOS Read More »
CAR — or “rate limiting” — is a method for managing unwanted traffic on your network and making sure it doesn’t affect important traffic. Essentially, CAR controls the bandwidth of a certain type of traffic, and an access control list (ACL) defines which traffic it controls. Once you’ve created the ACL, you can set CAR
Committed Access Rate in QoS with Cisco IOS Read More »
As VoIP becomes more widely used in the enterprise, the number of voice calls traversing the enterprise WAN becomes larger and larger. Typically the use of a proper codec is implemented to reduce the amount of bandwidth a voice call requires. The most commonly used codec for WAN voice traffic is called G.729. While there
Compressed Real Time Protocol (cRTP) to Streamline Voice in Cisco IOS Read More »