Cisco 3925ISR w/SM switch L3

David Gallant · ‎07-13-2016

We currently have a Cisco 3925ISR with a 24-port SM switch module (SM-ES3-24-P). The switch is configured for L2 devices only using "router on a stick" config. Now we want to config one of the SM Ethernet ports as L3 and have the traffic routable to the rest of the network. When I checked the SM config guide it mentions the L3 capabilities but there is no sample config to follow. Google searches result in lots of frustrated people trying to figure out the same thing! :-)

So does anyone have any experience with this that they want to share?

Richard Burts · ‎07-13-2016

Typically you can not configure a physical port of the switch as layer 3. So what you need to do is to configure a new vlan, assign the switch port to the vlan, and configure a vlan interface with the IP address. You would also need to arrange routing so this port can reach other resources and that other resources can reach this address.

HTH

Rick

HTH

Rick

David Gallant · ‎07-13-2016

Thanks Rick for your response!

In the past on the NM-16ESW Ethernet switch card we could convert a port to L3 by using the "no switchport" cmd.

So I mocked up a setup in the lab using 2 - 3925ISR routers with a SM 24-port switch card in each. See attached PDF and router/switch configs. Right now either laptop can ping the router loopback over WAN ckt 1. Now I want to convert the WAN path to #2 using the SM switches. I'm not clear on how to do that...so do you have any guidance on the config to use?

David

Richard Burts · ‎07-14-2016

Your drawing shows ckt 2 as being switch to switch. But the gateway address is on the router and not the switch. The switch config shows one access port and one trunk port to the router. So there is only one connection and it is through the router. So it looks to me like you need to create ckt 2. Perhaps connect switch port to switch port? Perhaps try the no switchport on them. Or create a new vlan for them.

It is not clear to me whether you want to do routing on the switch module or to keep it layer 2 and route on the router.

HTH

Rick

HTH

Rick