Router to switch L3 connection

[ManInTheMiddle]

Hi all,

I currently have a router on a stick configured for a router to switch connection to route VLANS but I want a better way to do it. 

First off I have an ASR router and WS-C3560X-48 layer 3 switch. I would like to have a layer 3 connection connecting them both. Can I advertise the VLANs from the router to the switch via BGP and configure the switch with subinterfaces per encaps dot1Q VLAN? The entire switching network is L2 but I just want to get the VLANS to the switch without using a router on a stick design. 

Any feedback is greatly appreciated. 

[Georg Pauwen]

Hello,

EDIT:

actually, the 3560 DOES let you configure subinterfaces. Just configure a port as 'no switchport', it then behaves the same as a router interface. By enabling 'ip routing' on the switch, it effectively becomes a router, and you can connect it to your ASR on any common subnet...

Does that make sense ?

[ManInTheMiddle]

Super, yeah makes sense..

Enabling ip routing, will that effect the current state of the switch? Currently it's part of a 4 switch L2 network and I really don't want to isolate the switch in any way. So my aim here is to send the VLANs to the switch and not disrupt the current network although it will prob drop while SPT reconverges but that's fine. 

[Georg Pauwen]

Hello,

when you enable 'ip routing' client traffic between different Vlans will be disrupted until you configure the subinterfaces. That is because the 'switch' will be doing the routing, and not the router. I would suggest that, if you do not want any interruption, to schedule this action for after hours...

[ManInTheMiddle]

yeah all work will be done out of hours. So, when work is complete I could still have the L2 switching network with one of the switches act as the router? I am thinking after all work is complete the network will perform the way it should.  

[Georg Pauwen]

Hello,

it should work...but as usual, something unexpected can always happen, so doing it after hours is advisable...

[paul driver]

Helllo

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@ManInTheMiddle wrote:

yeah all work will be done out of hours. So, when work is complete I could still have the L2 switching network with one of the switches act as the router? I am thinking after all work is complete the network will perform the way it should.  

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Note: with a collapse l3 access design you won't be able to have L2 vlans extend over multiple switch's each vlan L2/3 will need to reside on the same