Posts from ‘CCDA’
Just ahead of our brand new CCNA Voice live online bootcamp beginning this Monday, I thought it might be nice to provide an easy-to-follow graphic for those starting out in Voice (or on any other Cisco networking track). This graphic was from last year, but remains quite easy to follow for each and every Cisco track.
Be sure you have a high resolution set if you wish to see the entire thing, otherwise scrolling may be necessary.
Cisco had promised us Christmas 2010 editions of these new exams. Those dates have slipped again.
The new Cisco CCDA 640-864 DESGN and CCDP 642-874 ARCH exams are now scheduled to hit by January 31, 2011.
Both exams promise to test new material regarding virtualization and data centers. Stay tuned to see if these new exams do actually materialize. For those tracking such things – this is the third new date for these exams.
About the Protocol
- The algorithm used for this advanced Distance Vector protocol is the Diffusing Update Algorithm.
- As we discussed at length in this post, the metric is based upon Bandwidth and Delay values.
- For updates, EIGRP uses Update and Query packets that are sent to a multicast address.
- Split horizon and DUAL form the basis of loop prevention for EIGRP.
- EIGRP is a classless routing protocol that is capable of Variable Length Subnet Masking.
- Automatic summarization is on by default, but summarization and filtering can be accomplished anywhere inside the network.
EIGRP forms “neighbor relationships” as a key part of its operation. Hello packets are used to help maintain the relationship. A hold time dictates the assumption that a neighbor is no longer accessible and causes the removal of topology information learned from that neighbor. This hold timer value is reset when any packet is received from the neighbor, not just a Hello packet.
To start my reading from Petr’s excellent CCDE reading list for his upcoming LIVE and ONLINE CCDE Bootcamps, I decided to start with:
EIGRP for IP: Basic Operation and Configuration by Russ White and Alvaro Retana
I was able to grab an Amazon Kindle version for about $9, and EIGRP has always been one of my favorite protocols.
The text dives right in to none other than the composite metric of EIGRP and it brought a smile to my face as I thought about all of the misconceptions I had regarding this topic from early on in my Cisco studies. Let us review some key points regarding this metric and hopefully put some of your own misconceptions to rest.
- While we are taught since CCNA days that the EIGRP metric consists of 5 possible components – BW, Delay, Load, Reliability, and MTU; we realize when we look at the actual formula for the metric computation, MTU is actually not part of the metric. Why have we been taught this then? Cisco indicates that MTU is used as a tie-breaker in a situation that might require it. To review the actual formula that is used to compute the metric, click here.
- Notice from the formula that the K (constant values) impact which components of the metric are actually considered. By default K1 is set to 1 and K3 is set to 1 to ensure that Bandwidth and Delay are utilized in the calculation. If you wanted to make Bandwidth twice as significant in the calculation, you could set K1 to 2, as an example. The metric weights command is used for this manipulation. Note that it starts with a TOS parameter that should always be set to 0. Cisco never did fully implement this functionality.
- The Bandwidth that effects the metric is taken from the bandwidth command used in interface configuration mode. Obviously, if you do not provide this value – the Cisco router will select a default based on the interface type.
- The Delay value that effects the metric is taken from the delay command used in interface configuration mode. This value depends on the interface hardware type, e.g. it is lower for Ethernet but higher for Serial interfaces. Note how the Delay parameter allows you to influence EIGRP pathing decisions without the manipulation of the Bandwidth value. This is nice since other mechanisms could be relying heavily on the bandwidth setting, e.g. EIGRP bandwidth pacing or absolute QoS reservation values for CBWFQ.
- The actual metric value for a prefix is derived from the SUM of the delay values in the path, and the LOWEST bandwidth value along the path. This is yet another reason to use more predictive Delay manipulations to change EIGRP path preference.
In the next post on the EIGRP metric, we will examine this at the actual command line, and discuss EIGRP load balancing options. Thanks for reading!
Just as with the CCDP, Cisco has delayed the release of the new DESGN exam. The DESGN exam (640-864) is expected to be available on December 16, 2010.
Here are the topics promised fro the new exam:
Describe the Methodology used to design a network
- Describe developing business trends
- Identify Network Requirements to Support the Organization
- Describe the tools/process to characterize an existing network
- Describe the top down approach to network design
- Describe Network Management Protocols and Features
Describe network structure and modularity
- Describe the Network Hierarchy
- Describe the Modular Approach in Network Design
- Describe network architecture for the enterprise
Just a quick reminder that the CCDA and CCDP exams are updating to version 2.1 on November 8, 2010.
Our upcoming CCDP Bootcamp will reflect the new 2.1 exam, and we will be updating our CCDA Bootcamp in November/December 2010 as well. As always, customers that had previously purchased the CCDA Bootcamp will receive the updates free of charge.
Thank you so much for choosing INE, and enjoy your studies!
So many students have written me excited for the upcoming Cisco Certified Design Associate (CCDA) 5 day online bootcamp. In this blog post I want to provide everyone with a preview of some of the hugely valuable content in this course.
Early in the week of the event, we review a network health checklist from Cisco Systems. We take this one step further during the bootcamp and show you how to actually obtain these measurements without breaking your budget:
- Ethernet segments should not feature a sustained utilization of 40% or higher
- All Ethernet segments should be switched – no shared segments (hub-based)
- No WAN links should feature a sustained utilization of 70% or higher
- Response times should be generally less than 100 ms
- LAN response times should generally be 2 ms