| FAQ |
  |
| Networking : Tricky Ones : The Truly Challenging Interview Question |
    |
| Question: | When I go for my interview, I’m always asked about the difference between a router and a Layer 3 switch. So please, can you tell me what the technical differences are? |
| Answer: | I’m sure I’ll irritate some marketing people here, but from a basic, functional, technical standpoint, there is NO Layer 3 switch!!!
Look at the technical pieces. You have a switch. It switches. It works at Layer 2 and does its fancy data- link/frame stuff, and does it very fast! This is good. You have a router. It routes. It works at Layer 3 and does its fancy network/packet stuff, and depending on the model you have, does it very fast! This too is good! Then you have marketing people. They don’t discuss much technically, but they know how to sell things. You have design people too! They know far more about ASICs and ICs then I will ever proclaim to know, but they don’t know much about marketing. Putting these two groups together is very scary! What started out as a great combination of two SEPARATE things (a switch and a router) has suddenly become something akin to Frankenstein. It’s something new, built from the pieces of other common things we know and love! But that doesn’t make it something different! The base of an “L3 switch” is still a switch. It will do the same functions as other switches. There is actually a separate bus architecture for the L3 “stuff” that it does, and in most instances an actual daughterboard that the router is contained on. So what we have done is placed a router inside the switch. There is still a switching engine that works just like any other switch. There is still a routing engine that works like any other router. They happen to exist in the same box now, which saves rack space, makes things appear sexier than they did before, and gives people new and exciting ways to spend their money! Now a note! If you’re going to an interview, please don’t repeat what I just said word for word! Play nice with others and just explain the technical parts: It’s simply a combination of two previously separate items! Don’t forget that our routers have always assembled frames and remembered next-hop MAC addresses. Does that make them Layer 2 routers? I think not. Enjoy the power they bring, but don’t forget the basics are still the same. Just more horsepower! |
| last updated 01.03.2003 | |
user rating:  comments on ratings | |
| [previous FAQ] [next FAQ] | |
| List FAQ in this category | List categories | List all FAQ | List programs |
|