jasonlees wrote:
The network is growing, there are some performance issues but not extremely bad, probably will get worse with growth though. Really, just using a separate L2 switch for each subnet, nothing very complex but not a good configuration either. Using a 3560, that seems to be more in the cost range than some of the higher end switches. Would you think multilayer switching is overkill?
No, i don't think multilayer switching is overkill for a LAN. Yes you could buy a router instead but the forwarding rates on comparable switches are far better than routers because L3 switches forward packets in hardware. a 6500/4500 solution would be overkill but that's why there is also the 3560/3750 for smaller environments.
With 7 subnets currently + more if your network is growing a router is not really a good answer because of the limitation of the number of interfaces. An option for you may be to consider something like an ISR router with a switch module but the switch module is based on a 3750 so you still end up with a multilayer switch. And if you just buy a router you are going to be using subinterfaces without the additional modules. You are then limiting inter-vlan throughput because you are carving up a single interface for multiple vlans.
Using subinterfaces on a router to route between multiple vlans is called "routing-on-a-stick" and was really primarily used before the advent of L3 switches. If i was designing a LAN now and i needed inter-vlan routing i would not consider routing-on-a-stick. I would be looking at 2 options really -
1) ISR with inbuilt switch module. This could be a full blown L3 switch module as mentioned above or a L2 type switch module where you create vlan interfaces on the router.
2) A L3 switch such as the 3560.
Which one i would go for would be based on a number of factors but if a L3 switch did everything i needed for a LAN environment that is more often than not what i would go for.
Jon
