ROAS Sans Sub-Interfaces

[Matt Wilson]

Hi all. Fairly new to this game. I understand the router on a stick concept well. I was wondering if there were a way to terminate VLANs via a trunk link to a router without using sub-interfaces on the router. I'm thinking along the lines of using a trunk link on the router and using VLANs as the terminal IP addresses.

My setup is straight forward. A switch with PCs connected and divided up into various VLANs as expected. A trunk link on the switch ports these VLANs to a trunk link on the router. The VLANs on the router then do the routing.

I don't want to use sub-interfaces on the router as this will preclude the use of the other switchports from using the subnets.

I am using a Cisco 1941 with 2 x L3 ports and 8 x L2 switchports. I want to rout all this out to the internet via the EHWIC VDSL.

[Georg Pauwen · Accepted solution]

Hello,

your only option is to connect the switch to one of the L2 switchports. If you connect it to a layer 3 port on the router, you need the subinterfaces. With the switch connected to one of the L2 ports (and configured as trunk on both sides), you can use SVIs.

[Richard Burts · Accepted solution]

If you configure one of the L2 ports as a trunk, configure vlans, and configure vlan interfaces with IP addresses it should be able to route for those vlans, and any other L2 ports should be able to be configured to be in those vlans. 

[Matt Wilson]

Thanks for your help fellas, I'll give it a try. I thought you may have to somehow tie the router trunk port to the VLANs as you do with subinterfaces using the "encapsulation dot1Q xx" command.

[Richard Burts]

I am glad that our suggestions have been helpful. Thank you for marking this question as solved. This will help other participants in the community to identify discussions which have helpful information. This community is an excellent place to ask questions and to learn about networking. I hope to see you continue to be active in the community.