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L3 Switching and Router which is best

Hi Team,

I know this is a normal question, but i need some info on this. So plz share ur comments.

What is the main diff between L3 switch and Router. which is fast and why?

what are the adv'js and dis adv'js. Please share.



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L3 Switching and Router which is best

Hi Satya,

The usual answer that you will get is " That Depends on your requirement"

When you say faster, it also depends which thing you need to be fast; what i mean is whether you need packet to be switched more faster or the other L3 stuffs.

To make it more interesting and clear, I will say it depends what you requirement is depends on whether you need more faster Data Plane or more faster Control Plane.

Just as an example: Let assume that you want you build a route-reflector, which is catering to say 50 iBGP clients. In this scenario, you need Control Plane, i.e. more faster CPU rather than more faster Data Plane ( commonly addressed as backplane speed).




Re: L3 Switching and Router which is best


This is a generalisation for the low end switches/routers (fx 3750 series) and you will always find examples that is not accurat with this generalisation.

that said as a general rule it will apply.

As a general rule the L3 switch is a fast router on a local lan or a metro ethernet connection..


It lacks the ability to route other protocols than IP and it has a limited memory available for routingtables and that type of information. It lacks full advanced routing and it can not contain fx NAT and firewall ruleset. It does not handle other types of connections than some variation of ethernet. it can not be memory upgraded


in a local lan that has no need for advanced routing protocols and can utilise fx static routing, ospf and so on they are a very trong alternative with many ports/svi that

It is very fast and affordable compared to a true router routing the same speed.



Exspensive and slow (in comparision to L3 switch)


It can utilise any form of connection, (serial links, ethernet and so on)

It can utilise things like NAT, firewalling, ids, netflow  and such features (think I saw a figure of over 200 feature types)

It can have large routing tables.

It can utilise many different types of routing protocols

It can utilise many types of protocols other than ip (fx ipx/spx and so on)

It is expandable (ram memory and flash)

It is expandable by using different expansion cards.

so to short it out you can say

L3 switch is fast and inexpensive but does not know to much. the reason it is fast is because it does not have to be smart and that is the reason you can do alot of things in the ASICS (with hardware) instead of in the CPU (with software)

Router is slow and expensive but knows and can handle a lot. The knowing and handeling alot of diffferent variables, is very dynamic and thus made in software (CPU).

Good luck


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