Distance VS LinkeState Routing protocols

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Jan 7th, 2008
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I don't have much experience with configuring linkstate en distance protocols in real life, just in labs I do it. I am at CCNA2 now. But, what is the main difficulty of linkstate protocols? The configuration is almost the same of distance? right? Or is it the troubleshooting?



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shrikar.dange Mon, 01/07/2008 - 02:19
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the the main thing in having a link state protocols is that they are more complex to work with.And They eat up more CPU and memory of your router compare to ditance vector.

The configuration is also some what different than distance vector protocols.

In distance vector protocol each router depends on its neighbors for information, which the neighbours might have learned frm their neighbours, and so on, distance vector routing is osmetimes reffered to as "routing by rumor". Also the distance vector protocols can have routing loops and slow to converge.

In link state protocols each router originates info about itself,its directly connected links(state of those links) & directly connected neighbours.This info is passed around frm router to router,each router making a copy of it, but never changing it.

The link state protocols are loop free and fast to converge.

This is a very short explanation.Hope this helps.



Link-State such as OSPF is almost straight forward for small networks (single area) and you may configure it without the need of giving it alot of design effort. But as you know, OSPF is meant to run over large networks with tens or even hundreds of routers and links. The main issue with link state is that it is router resources intensive in means of memory and CPU because link state routers need to have a full view of all links within the same area. Here comes the need of dividing your networks into multiple OSPF areas and put in mind all related design considerations such defining area borders, neighborship, NBMA, route summaries... etc. This is only a brief overview as link state is a big topic.

Richard Burts Mon, 01/07/2008 - 05:21
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As you point out from a configuration standpoint there is much similarity between Link State and Distance Vector protocols. Especially in the fact that both type of protocols use network statements to identify the interfaces to include within the protocol they are similar. The differences appear in the way that the protocols operate and the ways in which you would approach troubleshooting for the various protocols.



bvsnarayana03 Mon, 01/07/2008 - 06:08
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Configurations: Given a scenario & to configure it for distance & linkstate. There's not much of difference. But yes there are some features supported by Linkstate & are not supported by dsitance vector. Some of these are wild card, stub configs & sumarisation(later on added to ripv2).

Operation: In this aspect, there are many differences:

- Link state are scalable to large boundaries & dont have a hop count limit like distance.

-Triggered updates of link state compared to periodic updates of distance is another advantage.

-hierarchial architecture of link state is another benefit which is not avail with distance protocols.

-Link state are CPU & memory intensive because of the trigered updates. However for stable networks its not an issue.

hope that clarifies.

pls rate all helpful posts.


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