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How to configure Rate Limit to stop bandwidth hogs

Have you ever had a low speed serial link get overrun by a single user hogging all the bandwidth? Well, there is a quick and easy way to prevent any type of traffic from using up an entire link - rate-limit.

To implement this feature, you simply type in rate-limit under an interface and specify a few parameters such as the allowable bits per second and the burst rate. However, if you do that it will rate-limit all traffic traversing the link which honestly the link will do on its own when traffic exceeds the available bandwidth. A more useful configuration is to include the access-group keyword in the command and point it to an access list that defines the traffic you want to rate-limit.

To demonstrate, I've configured two routers connected with a low speed serial link clocked at 128k. Without the rate limit configured, you can ping between them with no problems:

15 Open Source Tools for Windows Admins

Network World put together a pretty good list of free tools for Windows Admins. The tools range from Wireshark to VirtualBox. Check it out if you are looking for some free tool goodness.

How to configure multiple NTP time sources in Windows Server 2008 (R2)


Over the past few weeks, I noticed my computer's time was drifting several minutes behind. This actually caused me to be late to a couple different meetings because I kept working on my computer instead of leaving the house. Well, since it's a Saturday and I had some time to fix the problem once and for all, I wanted to share what I've learned since it took longer than I expected to configure NTP on a Windows Server.

It all began several months back when I setup a Windows 2008 R2 Server and thought "wouldn't it be cool if I set my desktop's clock to update from the server instead of a reliable external source?" So, I unwittingly redirected my desktop from its reliable to my server's ip address with the assumption the server was already getting it's time from a default external source. Hence the source of my lateness months later.

Fast forward to today. I figured it would be a quick 5 minute fix to remote into the server, find some sort of ntp settings tab in a properties window, then add my multiple servers. I should have known better than to assume Microsoft would have added such a logical GUI feature. 

After searching the Internet, reading through several Microsoft technet articles, and testing multiple configurations, here's what I've got...

Cisco Certified Technician (CCT)

The newest addition to Cisco's line of certifications is the CCT, or Cisco Certified Technician. Released in August of this year, the CCT certification has three different areas of focus:

Each certification focuses on the on-site maintenance and support of Cisco equipment in each specific area.

You might be wondering what is the difference between the CCT and the CCENT? Cisco explains that and several more questions in their FAQ, but for those not interested in reading through all of that, here's the basics...

Mobile CCIE Labs

If you are planning on going for the CCIE R&S or Security and you live in a country where the lab is not administered, it can be a challenge to get to the testing center, let alone pass the exam! Cisco has had a program in place to combat this very issue for quite some time called the Mobile CCIE Lab. The program allows you to register to take the lab exam in your city or one closer to you than in a foreign country. The benefits here, of course, are potential savings in travel expenses and missing less work ( even though you might not be missing it).

For a complete schedule of where and when the lab will be available, or if you are interested in learning more about this program, check out the official Mobile CCIE Lab page at Cisco's website.

Automatic 6to4 Tunnels

While reading up on IPv6 tunnel configurations, I came across this way cool video on configuring 6to4 tunnels. Keith Barker definitely knows his stuff on this topic and makes it interesting and easy to follow. Check it out:

How to configure an IPv4 GRE tunnel to carry IPv6 traffic

Continuing the review of the TSHOOT Topology, on the IPv6 network map there is a GRE tunnel that is configured between Router 3 and Router 4. This tunnel is in place to allow IPv6 traffic to traverse the IPv4 network. So, while reviewing the IPv6 tshoot topology, I decided to try out the tunnel configuration.

There are several ways to configure tunnels to allow IPv6 traffic to traverse IPv4 networks (and vice versa). This post will be focusing on a GRE tunnel configuration. If you want to review the other ways to create tunnels, i.e.  Automatic IPv4-Compatible IPv6 Tunnels, IPv6 Rapid Deployment Tunnels, and Automatic 6to4 Tunnels, I've included a link below to a great resource on Cisco's website that shows some great examples of other tunnels.

I threw together the following network diagram to provide a visual of what we are configuring: 


Cisco SG100-16 Unmanaged Switch

Need more Gigabit Ethernet? Don't need it to be a managed switch? This 16 port 10/100/1000 Cisco switch might be a quick and easy solution for you.


The Cisco SR2016T 16-Port Rackmount 10/100/1000 Gigabit Switch (A.K.A. SG100-16) is currently listing for below $200 USD and has several appealing features:

How to configure a Cisco router to be a frame relay switch

If you are studying for the TSHOOT exam, it is a good idea to familiarize yourself with the topology. I've been working on creating a lab that mocks the TSHOOT topology, and it has forced me to recall how to setup a Cisco router to act like a Frame Relay switch. 

Here is the topology that I've built. As you can see, it closely resembles the topology that Cisco has provided on their site. Since their doc doesn't provide specific DLCIs, I've used the most logical numbers I could think of.


The first step in configuring a Cisco router to act like a frame relay switch is to enable frame relay switching:

End of Life Announced for Cisco 7200 NPE-G1

Cisco this week has announced the end of sale and end of life dates for the 7200 Series NPE-G1 Network Processing Engine. This is an older routing engine that is definitely showing its age compared to newer platforms that are available.

The last day to buy the NPE-G1 is February 27, 2012. Last day for hardware support is February 28, 2017. The recommended upgrade path is the ASR1000 series.

Full details are available in the official announcement.

Windows 8 to include native support for ISO and VHD files

Just read an msdn blog post that reviews a cool feature to be included in Windows 8. Windows will now natively support ISO and VHD files! This is definitely nothing new, as 3rd party utilities have been available for years to provide this functionality in Windows. Alternatively, Linux has had the ability to mount ISOs since the dawn of time.

The good news is you will no longer have to go through the trouble of installing a 3rd party app, it'll just work.

Juniper's Tesla Motors Commercial

I realize this is a Juniper commercial, but the car is so cool I have to share. Check it out...

Free Cisco Press Chapter - Configuring Policies, Inheritance, and Attributes

Studying for your CCNP Security? If you are, or if you simply want to learn more about VPNs, take a look at this free chapter from Cisco Press on Configuring Policies, Inheritance, and Attributes.

This is straight out of the CCNP Security VPN 642-647 Official Cert Guide. According to Cisco Press, the chapter covers the following topics:

  • Policies and Their Relationships
  • Understanding Connection Profiles
  • Understanding Group Policies
  • Configure User Attributes
  • Using External Servers for AAA and Policy Assignment

Give it a read if you got your certification cross-hairs fixed on the CCNP Security.

Cisco Power Calculator

If you are ever designing a network or deploying a new switch that will be providing Power over Ethernet, be sure to check your power draw with the Cisco Power Calculator (CCO login required):

You start by selecting the type of switch you are deploying. Then you can choose how many of each type of device you will be plugging into your switch and it will tell you how much power will be required.  Here is a sample of some of the devices they let you choose from:

  • 7961G-GE - 0.3071 amps (12.9W)
  • AP-1200 with a+g radios (12.4W)
  • CP-7971G (14.9W)

Also, if you are deploying non-Cisco phones or APs, there are several IEEE compatible devices listed toward the bottom of the list:

CCNA Official Cert Library, 3rd Edition

The latest and greatest CCNA Certification Library is available for pre-order. The seasoned author, Wendell Odom, has updated the material from previous releases with new content and exercises.

In addition to the books to prep for ICND1 and ICND2, the library includes a test prep engine, a network simulator, and videos. With 1500 pages included, this package is a great resource for anyone starting out on their CCNA journey.

The library package is scheduled to be available October 14, but you can pre-order today.

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