How L3 switching works.

mahmoodmkl · ‎07-10-2007

Hi Guys,

I am little bit confused about the term layer 3 switching i.e hardware based routing.can anyone explain or proivde a link which explains this.

Thanks

Mahmood

Jon Marshall · ‎07-10-2007

Hi Mahmood

Layer 3 switching as you say is routing done in hardware as opposed to software. Generally speaking a router will route packets in software ie. the intelligence to make the routing decision is contained within the IOS code.

A layer 3 switch however has dedicated ASIC ( Application Specific Intergrated Circuits ). These are a bit like the CPU of your PC except that they are specialized in what they do and hence more effecient. On a L3 switch it these chips that route the packets.

TO be honest you have pretty much summed up the major difference in your question and L3 switching was used primarily as a marketing term when it originally came as everybody knew Layer 2 switching was fast and routing was slow.

HTH

Jon

royalblues · ‎07-10-2007

This link might help

http://www.ciscopress.com/articles/article.asp?p=102093&rl=1

Narayan

mohammedmahmoud · ‎07-10-2007

Hi Mahmood,

In addition to Jon's and Narayan's wonderful input, please check this article, i think it would be very informative:

Layer 2 and Layer 3 Switch Evolution

http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_1-2/switch_evolution.html

HTH,

Mohammed Mahmoud.