Work Stuff – More Studying – Collapsing the Data Center


I created a task for myself at work, not that my work load hadn’t already been enough.

I wanted to implement Active Directory authentication on our Alcatel-Lucent equipment using a Windows Server 2008 R2 server acting as an NPS server. I wasn’t able to find much documentation on this at all on the web or at Alcatel Unleashed or even Alcatel’s configuration manuals or user guides. They were, however, nice enough to provide me with the Vendor Specific Attributes(VSA’s) that needed to be added to the RADIUS server to provide the appropriate information to the device. I will post the complete write-up on that at a later time, as I am still writing the documentation at work and I want to finalize it before I post it.

On a better note! I’ve been doing a lot of CCNP preparation as of late, and I am starting to feel more and more comfortable with the concepts and application of the material. I’ve worked my way through EIGRP and OSPF and I have moved on to route distribution. The more I read and the more I work in my home lab and GNS3, the more thirsty I become for learning and digesting anything network oriented. Using route-maps and ACL’s to efficiently distribute routes between different domains or to assign specific metrics to routes to make it even more efficient! I find myself analyzing everything at work to see how I can make it more efficient. Which can’t be a bad thing, and they certainly benefit from it.

OK, I’m sure you’ve heard enough in my posts about my studies. Let’s talk about some industry buzz for a while. Collapsing the data center, in a good way. In the past, traditional networks required an abundant use of distribution layer switches to communicate with the core layer of the network. The article states that there isn’t as much of need for the distribution layer anymore. That the access layer switches could communicate directly with the core for core services. As we move further into the future and the more I work with these types of technology, the more I realize that there may actually be some logic to this theory. In the past, equipment couldn’t be considered as reliable as it today. Decreases in power demand, footprint and cost, and increases in reliability and performance are starting to allow devices to last longer and produce better results. This leaves us with the option to start eliminating some distribution layer devices and start uplinking access devices directly to the core.

Most arguments I’ve heard against this idea addresses redundancy and availability. But, if you have an access layer switch uplinked to a distribution layer device which then uplinked to the core, and that distribution layer switch were to fail, you’re still left with the same results as if the access layer switch failed. No connectivity.  So, the idea of less complexity and more performance is always something we’re all keen on as network junkies.

Another topic I’d like to discuss in a later post would be “cloud” technologies. While good in theory, I think the world is in for a bit of an eye-opener when we really start moving heavily toward companies who provide a cloud service. I see it as one giant security threat. Even with the ideas of public, private, or hybrid clouds. But, I digress. I will write that up in another post.

Though I’m still new to the in depth studies and theories of networks, I still strive to make the best judgements with what I know. Please feel free to add input or correct me in any of my statements.

Thanks for reading!,



EIGRP variance

Cisco’s proprietary routing protocol, EIGRP, offers and interesting tidbit of functionality to the network that decides to run on entirely IOS based routers. This little tidbit is known as the EIGRP variance command. What this function does, is allow for unequal cost load balancing on a router.

Please see Diagram below:

You’ll notice that the HQ router is connected to both remote office via some sort of serial based medium. One interface bandwidth being 128Kbps and one being 256Kbps (I know, not a whole hell of a lot of bandwidth, but this is just for ease of example). Along with that, the remote offices are connected using a FastEthernet standard at 100Mbps.

You’ll notice that Remote Office – 1 has network connected to it. Now, if all routers in the diagram are running EIGRP and are all fully converged, the HQ router will have a route installed in it’s route table for the network. Due to the low bandwidth on the 128Kbps link directly to Remote Office – 1, router HQ is going to install the HQ <-> RO2 <-> Switch <-> RO1 route into its routing table strictly because the cost of traversing that 128Kbps link, as opposed to the 256Kbps link and then the 100Mbps link between the two remote sites, would be far more costly on the time it would take for the traffic to reach it’s destination.

That being said. We all know, in the IT industry, we’re looking for newer and faster ways to get data from point A to point B. And we all know a little bit about what load-balancing is – Utilizing more than one medium to transport traffic from A to B at the same time – balancing the traffic 1-to-1 across multiple links.

Well, Cisco decided that the whole “only equal cost load balancing” model was a little too restrictive. So, they took it upon themselves to not only create their own routing protocol, but add a few little tidbits of functionality to it that truly make it their own. And this is where the variance command was born.

The variance command allows you to load balance the traffic across unequal cost paths, as opposed to the traditional load balancing across only equal cost paths.

If we refer back to the diagram above, we can see that we can now issue the variance command on the device for that particular instance of EIGRP on the HQ router. We will call the multiplier (n) for the sake of the following example.  To keep it simple math wise, if we entered the variance 2 on the HQ router, the router would then include routes with a metric of less than 2 times the minimum metric route for that destination. What that means is, once this command is issued, the router will look for routes to the network that are proportionally unequal to the metric of 2 defined in the variance command. (ie. 128Kbps is exactly 2 times less than 256Kbps)

A little tricky at first, but once you actually sit and think about it, just make sure that you have your math right before you enable the command, and watch the previously useless routes come to life and allow even more optimization to your network. 🙂

Another Day, More Studying.

Like I said, I’m going to try and keep this page as up to date as possible with anything and everything that crosses my mind through my studies.

I managed to complete the first couple sections of my CCNP ROUTE book which covered Planning, EIGRP and OSPF more in depth than anything I’d seen in my CCNA studies. I truly understand how and why the industry is hurting for people who really do know how to plan and execute and maintain a proper network these days. There are many, many factors to be taken into account while planning and designing a network. Let alone the actual configuration and deployment! I haven’t had to ability to work on some of the systems discussed in the book, but I can truly see the power behind the protocols of today’s networks.

I did know a little bit about the variance command previous to reading and playing around with it on my lab equipment, but to bring up a 128kbps and 256kbps WAN link between two routers and issue a multiplier of 2, and actually watch the load balance happen in real time was quite the eye opener. +1 to EIGRP over OSPF for that definitely. Now if we could just do something about the draw-back of being a proprietary protocol!

Aside from that, learning about the different LSA Types being advertised in OSPF LSU’s was also interesting in and of itself. LSA Type 1 including all of the directly connected interfaces on that router and all other known routes for that area, really brought a deep understanding of how OSPF maps the topology of a single area in OSPF. Leading to the Type 3 LSA’s being advertised to other areas through the ABR and summarized(manually of course) for efficiency. Again, something I put together in my lab and brought a deeper understanding of the protocol.

Over all, I am enjoying my studies for CCNP. I plan to, time allowing, put together diagrams of everything I work on as I go. Whether is be on my personal rack of equipment or using GNS3 – though my computer doesn’t really handle it very well as it’s a bit lacking in the processor department!

I am working on giving my blog a little eye candy for the few readers that I have. You’ll notice the new theme. A freely provided theme from WordPress, as I spend too much money on lab equipment to drop the cash on a Premium template.

As a side note, at work, we actually use Alcatel-Lucent products for all of our networking needs, and all of my experiences with Cisco equipment helped me to get up to speed on what Alcatel refers to as AOS – the IOS of their equipment. I will bring more on that later, and the difficulties I can endure while studying one platform and working in a live environment on another. I find myself mish-mashing commands between the platforms, which makes for quite the show when I’m smashing my keyboard and yelling out loud – “Why is this command not working?!” – and ending up realizing I’m typing a command for the other platform.

Feel free to leave some feedback, especially those who have taken and passed the CCNP as I am open to any and all constructive criticism that can help me better myself.

Thanks for reading!


Long time, no post.

Hello Everyone,

I haven’t posted in quite some time, as I’ve been studying quite a bit in either anything Network related or anything related to my current enrollment in college. Working on my BSIT – Information Security and Assurance. I may be keeping things short and to the point as of late, with the newest addition of my family set to arrive in August, 2011. Another boy!, making that 3 strikes on the little girl. I guess I’m out, but not according to my wife.

Anyway, I wanted to talk a little bit about an interesting problem I was presented with from a friend of mine. He was setting up a 2 link ether-channel on a Cisco 4500 series and ran into an interesting issue. You can see in the image below that the link actually negotiated what looks like a sub-interface on the ether-channel.

LACP sub-interface negotiation

This was a little odd, as I’d never seen an ether-channel negotiation produce a sub-interface. So I did a little bit of digging and found some interesting information on what could have possibly happened.

It seems that the alpha-numeric number/letter combination assigned to the Po19A does indeed indicate a mis-negotiation of the link on the end of the 4500. I would imagine that this could be anything from a Speed / Duplex mismatch to STP finding it as a “redundant” link and causing it to re-negotiate the link on the fly. This, of course, would all be done using LACP, as this is the protocol that is used for negotiating a Link Aggregation that isn’t statically configured. I wasn’t able to produce this on my lab equipment, though I am still trying occasionally. If anyone reads this and has any possible insight as to what could have caused this, it would be greatly appreciated. For now, I will stick to my own hypothesis.

On a different note, I was able to take and pass my CCNA exam on May 11, 2011. I passed with a score that makes me happy and with a considerable amount of time left, so I definitely feel accomplished on that end. I also picked up the CCNP Certification Library for around 100 dollars off of – much to my wife’s dismay. I get the feeling she thinks I bury my head in too many books and spend too many hours in my dungeon while teaching myself all of this information. But she has been incredibly supportive, so I cannot complain.

CCNA Crest

I plan to keep updating this as I progress through my CCNA Security and CCNP and all the way to CCIE, studies. I will also update it with little tid-bits of things I learn or stump me in the field to see if I can get anyone’s opinions on these matters.

Until Next Time,