Setup VLAN subnets on router or switch?

[abraxis]

I currently an running a fairly old 3825 router with an internal 48-port FastE switch card doing layer-3 routing.  I have the responsibilities split between them with the 3825 doing BGP on a /19 public network that I own, and the switch segmenting that into /30 VLANs that I assign to individual servers, with switchport access on individual ports to ensure they can't claim IP addresses outside their assigned range.

I'm wanting to upgrade my network with a ISR4431 router and a stand-alone 48-port GigE switch.  My question:  Can I setup the VLANs on the router and leave the switch in Layer-2 mode just doing switchport access?  Or do the VLANs need to live at the switch level?

Thanks

[BradEast1]

Should be able to do it either way. You can use sub-interfaces on the router or SVI's on the switch.

[Julio E. Moisa]

Hi

If you have an Ether Switch module, yes you can create VLANs on the router and also create the SVI there. 

[abraxis]

In my new configuration, I don't have the etherswitch module (that was my previous setup).  It is just a ISR4431 (which I have 2 free GigE ports remaining).  The router has much more horsepower available to it than the switch, so I was wanting to offload as much as I can to the router.  Also, I'd prefer to keep the major configurations in the same place.

[paul driver]

Hello

As suggested create sub-interfaces for the vlans on the ISR and trunk the port on the connecting switch to the new rtr and give it a mgt ip/subnet mask/D/G  for remote mgt ( if applicable)

Its what is known as a "router on a stick" setup

res
Paul

[Joseph W. Doherty]

Yes, although your 4431 may be more powerful than your 3825, the 4431 will likely come in a very, very distant second to any L3 switch doing LAN routing.

For performance, do LAN routing on a L3 switch and reserve your router for WAN routing.

Oh, just another answer to your question whether your router can do all the LAN routing and keep using your switch just as a L2 switch, yes you can, although normally you would still define VLANs on the L2 switch, just not define any SVIs or other L3 config info.