Switch to L3 Switch

Question: When building out a new network at what level do you change your layer 2 switches to L3 switches? Let me explain more.

I'm having a had grasp of when when in a medium to large network do i do this or do i not need to do this at all.

Picture this:

You have edge routers serviing the WAN and internet.
Then you have a couple or Core L3 switches.
Then you have some large closest switch. Each closet switch is something like a 4500 series, of which you have clients connected to this. You then have a bunch of smaller switches that clients and other devices are connected.

Do you make the 4500 routeable or keep them as L2 switches?

In the scenario above all the servers are in the core, so is there really any point in making those 4500 L3?

Hope i didnt confuse ya all.

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Comments

chmorin

I'm moderately sure the only switches in our network that use L3 technology are in our core. I'm not sure if that answers your question.

That being said, you probably could make them L3 and it wouldn't hurt anything.

ColbyG

It depends on your design. If you're running L3 to the access layer then the 4500 closet switches in your example would be routing.

Our network is L3 from the distribution layer up. Our closets are all L2 with each switch connected to both distribution switches via a trunk. At some point I'd like to see our network move to L3 at the access layer (death to STP!), but I don't think that will happen any time soon.

Sepiraph

ColbyG wrote: »

It depends on your design. If you're running L3 to the access layer then the 4500 closet switches in your example would be routing.

Our network is L3 from the distribution layer up. Our closets are all L2 with each switch connected to both distribution switches via a trunk. At some point I'd like to see our network move to L3 at the access layer (death to STP!), but I don't think that will happen any time soon.

That'd be very expensive. Usually single/dual core L3 switch is the most common design for a relatively large LAN site.

ColbyG

Sepiraph wrote: »

That'd be very expensive. Usually single/dual core L3 switch is the most common design for a relatively large LAN site.

Our network is already equipped to handle L3 to the access layer (sounds like that's what Matt is saying too). Most of our closet switches are 3560s or 4500s. Some are 2900s and would need to be replaced, but that's a small percentage.

I'm not sure what you consider "relatively large", so I can't say what is common there. I work for a very large enterprise, and common for us means very little L2 switches on our main campuses or at the branch sites. Most all of our client machines connect to an L3 switch. So L3 to access wouldn't cost us much monetarily. Redesigning and reconfiguring thousands of switches would be rough though.

Cyanic

ColbyG wrote: »

Our network is already equipped to handle L3 to the access layer (sounds like that's what Matt is saying too)

Ditto here, we route from distribution. I don't think we even have any layer 2 switches left.

We had STP problems in some buildings when we still ran 2950Gs there.