interVLAN with a L3 device vs Router-on-a-stick

Hi all,

I'd like to know why people would prefer one over the other of the above. In other words, would you rather deploy a L3 switch, enable 'ip routing' and use it to route between VLANs or would you rather trunk a switch to a router (router on a stick) and why? From people's experience, which is 'better' and why? I believe reasons for using one an not the other would include cost etc but aint sure..

What I'm trying to do?

basically. i have two VLANs and would like to route between them, whilst I'd prefer to turn on the routing feature on the 3550 device and use it to route between VLANs, I cant justify it. Of course, I could say something like since the L3 device has this feature I might as well use it but we also have a router so not sure...

Thanks for any inputs.

PS. the design is hierarchical & intervlan is to be configured at the distribution layer.

Layer 3 switches were introduced as a technology to improve on the performance of routers used in large LANs. The main difference between Layer 3 switches and routers lies in the way hardware is used to build the unit. The hardware in a Layer 3 switch is a hybrid mix of typical switches and routers, it replaces some of the router's software with hardware to give better performance. However, they typically don't come with any WAN ports. As far as I know, Layer 3 switches often cost less than routers.

On the other side, routers can have the full range of extended routing features. Such as extensive QoS, NBAR, IPSec, Security features etc. NOT that I know what I'm talking about . Routers are usually better suited as edge devices were you have both LAN and WAN services that need routing between them.

For your case, if you don't need any WAN ports/services, then I'd go with the layer 3 switch routing. It will perform better under high load than a router on a stick.

SOlo, thanks for the post. In additon to what you've said, would I be right to say that using an external router takes away the extra "burden" of routing from a L3 switch. But they should have been designed to cope with this right?

Any more contributions appreciated.

SOlo, thanks for the post. In additon to what you've said, would I be right to say that using an external router takes away the extra "burden" of routing from a L3 switch. But they should have been designed to cope with this right?

That's valid. But as you said, L3 switches are designed for this. So the overall performance that you'll get is probably better with the L3.

By the way, you probably wont notice a performance deference if your traffic load is lite. The deference is more evident at medium to high load.