Difference between Layer 3 Switch & Router

[okanyilmaz]

Could you tell me what are the differences between a router and a layer 3 switch?

 

[sharb]

Layer 3 switch has routing and switching capabilities.
but a router just routes the traffic and can not be used as a switch.

 

[marsd]

;-) Can be used as a bridge tho....
so not totally true..but 90% right.

 

[ronr101]

Sharb is correct. I would add... in moderm networking, a router is usually an edge device (LAN to WAN connections) with a small number of ports on it (one or two ethernet ports and one or more serial ports). It has low performance but great flexibility in the protocols it supports (IP, IPX, Appletalk...) A layer 3 switch is usually a core or distribution device with a large number of ethernet ports. The supported protocol(s) are usually limited to IP and sometimes IPX. This device has blazing fast performance, but is limited in it's flexibility.

 

[wybnormal]

Hold it... A router most certainly can switch depending on the model. remember something called CEF? Cisco Express Forwarding?? This is a form of fast switching which takes place at layer 3..

http://www.cisco.com/warp/public/cc/pd/iosw/iore/tech/cef_wp.htm

Normally a router will hold the entries in a cache and then decide where to route them.. A switch will do that for the first.. but after that, it's switching all the packets for the datastream. All occurs at layer 3 PACKETS.. unlike a normal switch which operates at layer 2 FRAMES..

If I had to make a distinction.. I would say that a layer 3 switch takes the first packet, builds the switch table/path from it and then switches the rest of the data stream. The router on the other hand, looks at each packet then routes it to the next hop. The big difference is the switch will be ALOT faster.. but like some pointed out.. it will be more limited to what it can do other then switch.

This short answer grossly simplifies all of it but it gets the point across that you can not make a blanket statement any more one way or the other. It's just not that simple in todays networks.

Also, on the 6500s, 8500s, the MSFC is a *switch* and a *router*.. so it's not just router with split personalities.

and the list goes on...

MikeS Find me at

http://www.packetattack.com

"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin

 

[onyx4000]

The short answer is, a router routes packets via software, a layer 3 switch routes via hardware. They both have a "switching" function not really to be confused with layer 2 switching, but the internal switching that a router must do to get a packet or a frame from one interface to the other.

 

[onyx4000]

The short answer is, a router routes packets via software, a layer 3 switch routes via hardware. They both have a "switching" function not really to be confused with layer 2 switching, but the internal switching that a router must do to pass data from one interface to the other.