So who said that Cisco Network engineering courses had to cost thousands.

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Commsupport Network is the original and still the only Network engineering company run by network engineers with courses taught by network engineers.

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So apart from our fantastically low prices why consider training with us

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Our courses focus on the really important practical engineering knowledge you'll need in the real world. The knowledge that'll stand you out from the crowd.

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Classroom based & Live On-Line Classes

Sign up for today to a Classroom based CCNA course with Commsupport and you can join in our live twice weekly on-line webinar classes Live on-line revision sessions

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Free Course Re-take Until you Pass

We offer the only unlimited free course retake policy in the industry, you can retake your course until you pass free of charge.

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Comprehensive Hands-on Labs

We make sure that our our Hands-on labs are laid out to assist you in understanding exactly what you are doing every step of the way. Download a copy of one of our CCNA classroom lab workbooks our hands-on labs are the only labs in the industry which will guide you through the everyday common configurations you will encounter in the real world an in the exams

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Great Practical Hands-on Lab work and our Break/Fix™ sessions

We take pride that on every course we run we are teaching you network engineering, making sure we do this by having the most comprehensive and detailed hands-on labs exercises in the U.K, also we are the only school to use the Break/Fix™ training methodology, you build it we break it,you fix it!

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Industry Innovators

Everyday we make sure that we improve our offering from making all of our own CCNA and CCNA Voice videos to now offering our students Live on-line webinar sessions courses.

You never stop learning, we never stop innovating. Learn why we believe it is important to us to lead the market

We are so confident of what we can do for you that we offer our free one day introductory networking courses. Come and sit with us and see for yourself and learn something new along the way too. Click here for more details of the free one day course

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You can now subscribe to our Commsupport events news letter, we will keep you up to date regarding more free webinar sessions and lots more.

CCNA Training – OSPF Costs

As a CCNA / CCNP candidate you are expected to understand how to set and interpret the OSPF cost function on your Cisco devices

During your career as a Cisco network engineer you will have to deal with setting and manipulating the OSPF costs on an interface.

OSPF uses a metric called “Cost” to calculate the metric of path. The cost is a cumulative value which is an incremental metric.

The cost is as a default based on the bandwidth of the interface. The Higher the interface bandwidth the lower the cost that is associated to that interface, to see the cost that is assigned to any given interface which is participating in OSPF issue the following command:

Router# show ip ospf interface

The output of this command will show the current cost given to this interface. The costs of the interface is calculated by taking the bandwidth of the interface and dividing this number by a value known as the “auto-cost reference-bandwidth”. This auto-cost reference-bandwidth is an integer used to calculate a standard metric across OSPF and is set to 100,000,000. The cost is calculated as follows:

100,000,000/BW

If the interface bandwidth is 10Mbps, then the resulting cost would be 10:

100,000,000/10,000,000 = 10

If the interface bandwidth is 100Mbps, then the resulting cost would be 1:

100,000,000/100,000,000 = 1

The next example reveals some deficiencies with the auto-cost reference-bandwidth set at 100,000,000. If we had a 1Gbp interface it’s cost will be calculated by OSPF to be the exact same number as that for the 100Mbps interface.

100,000,000/1000,000,000 = 1

The same would apply for higher speed interfaces such as 10Gbps interfaces which would also be interpreted by OSPF as having a cost of 1, since OSPF cannot define interface costs as an integer part of a decimal number i.e. 0.5 or 0.125.

So that OSPF may be able to calculate the cost of an interface based on the bandwidth of the interface with great accuracy we will need to change the value of the auto-cost reference-bandwidth value from 100,000,000 to a greater value.

To change the ACFB use the following commands:

router(config)#router ospf 1

R2_4(config-router)#auto-cost reference-bandwidth 10000

% OSPF: Reference bandwidth is changed.

Please ensure reference bandwidth is consistent across all routers.

The auto-cost reference-bandwidth now has a value of 10000,000,000 (The value is set in Mbps), therefore now the OSPF process will view the 100Mbps interface as having a cost of 100, 1Gbps having a Cost of 10 and 10Gbps a cost of 1, another point worth mentioning is that the router will prompt you to make sure that the auto-cost reference-bandwidth value is set consistently across all your routers.

Note: The cost given to a path is added to the metric only when the route is received inbound on an interface, not outbound, therefore should you wish to alter the cost of the path you must do this on the inbound interface.