IP routing with multi-layer switch: what if you have *many* multi-layer switches?

[omegaamigo]

I've read many IP routing examples where a single Layer 3 switch is used as the router in a network environment where all other switches are operating just at Layer 2. That's fine, I understand that.

However, what about if one has many Layer 3 switches?

Does one (a) simply choose one of the Layer 3 switches to be the router, or (b) do something more cunning, making use of the Layer 3 facilities of the other switches?

In the networks I'd be working in, the ports associated with each VLAN are fairly evenly scattered across all switches.

My thoughts on this stem from this problem: If one uses the simple approach of Choose Just One Switch To Be The Router, then all cross-VLAN traffic needs to pass across the LAN to that switch in order for routing to take place, which seems inefficient. As the size of the LAN grows, it becomes increasingly inefficient.

So, is the Just Choose One Switch To Be The Router approach the only option?

Comments welcome! Thanks.

 

[stubnski]

Hi,

No, you can have as many L3 switches in your network as you want. Every network is designed differently to meet the needs of the business. If your business requires you to have L3 routing in multiple places then design it that way. L2 is faster and cheaper than L3 so keep that in consideration when designing your network.

I would recommend you research routing protocols if you are planning a multi L3 switching environment as it will make your life much easier if you plan and implement routing protocols from the beginning.

 

[omegaamigo]

Thanks for the reply!

Multiple, separate routers I can understand and that might be a possible approach.

My CCNA didn't cover this: is there any way to make an *entire network of L3 switches* behave as a logical whole, with regard to routing? Or is the correct approach to configure each one separately and use routing protocols to make the configuration simpler and more scalable?

 

[stubnski]

Hi,

You will need to configure each one separately and use routing protocols to update the route table.

Here are a few links from Cisco about LAN design - here and [link

http://www.cisco.com/c/en/us/td/doc...ium_Enterprise_Design_Profile/MEDP/chap2.html

]here[/url]

 

[omegaamigo]

Nice one, thanks