Router on a stick

alliasneo

Hey guys, New to CCNP Switch!

I'm just looking into a layer 3 switch config and I have some questions. If I configure a layer 3 switch with say 3 or 4 vlans then then switch will be able to route between the vlans itself right?

So if I have this set up:



Would I still need to configure sub-interfaces on the router so that the PC's can get out of their VLAN and across the network? Or would you generally not connect a L3 switch to another router like this?

The reason I'm asking is because I thought that router on a stick was when you don't have a L3 switch in the network but when you do I can't figure out how you would get the PC's to the router?

Thanks

drkat

Quick answer... the L3 switch will do the core routing and the router will do the edge routing.. so in L3 switch you would have a default route to the router, so no.. no sub interfaces are needed.

Long answer?? RoS is yes when you have a Layer 2 switch and you need the router to route between vlans.. in this scenario the L3 switch will handle it and only send traffic the router when it needs to get out. The router would just route to the L3 switch

NetworkVeteran

alliasneo wrote: »

If I configure a layer 3 switch with say 3 or 4 vlans then then switch will be able to route between the vlans itself right?

Yes.

Would I still need to configure sub-interfaces on the router so that the PC's can get out of their VLAN and across the network?

No.

Or would you generally not connect a L3 switch to another router like this?

This is fine, if two l3 devices satisfy your business needs better than one.

The reason I'm asking is because I thought that router on a stick was when you don't have a L3 switch in the network

A router on a stick involves a router connected to a switch via a trunk link (the stick) with the purpose of performing inter-vlan routing.

but when you do I can't figure out how you would get the PC's to the router?

A L3 switch is very much like a router. The L3 switch routes the packet. You have all the usual options including routing protocols, static routes, and default routes. Although, technically, to get from the PC to the router, configuring routes on the l3 switch is unnecessary.

You would normally use DHCP to configure the PCs' default gateway.

alliasneo

Thanks for the responses. So I could just configure a static route to the router (which would be fine) or a routing protocol to get out of the LAN?

networker050184

Yep, you just need a route. Doesn't really matter how it gets it whether its static or a dynamic protocol.