3850 stack with ISR4431 etherchannel configuration

[Kn1ghtR1d3rOfD00m]

Hi team, 

Just wanted to ask you how can I make an etherchannel between the 2 stack cisco switches 3850 and the ISR4431/K9?

Im kind of confused I know that in some other post it is possible but never saw any config and Im not fully aware of how to mix both things up, 

is it layer 2 or layer 3 that I need to configure in both ends?

anyone has a sample config? I wish I could test in packet tracert or something, but if someone has already made it, can you provide me with some ideas?

attached you will find the topology in which I want to have the router with its loopback 1.1.1.1 reachable from the other side of the stack where I have connected the core switches to the stack layer 2 switches. 

but Im not really sure how it will go, can the following work?

switch:

int gig1/0/2

channel-group 1 mode on
switchport mode trunk

exit

int gig2/0/2

channel-group 1 mode on
switchport mode trunk

exit

router config:

interface port-channel1
ip address 10.10.10.1 255.255.255.0
exit

interface GigabitEthernet0/0/01- 0/0/2
channel-group 1
exit

[Reza Sharifi]

Hi,

Yes, you can create a Po between the switches and the router (see link for an example). It has to be layer-3 Po, as the router does not support VLANs. So, your config example looks correct.

https://www.cisco.com/c/dam/en/us/products/collateral/routers/3800-series-integrated-services-routers-isr/prod_white_paper0900aecd806f698a.pdf

Are the 3850 switches going to serve as layer-3 (core)? If that is the case, you want to terminate all your vlans on the core, and then use a layer-3 Po to connect to the router. If this is a small network, you can simply use static routes between the core 3850s and the router.

HTH

[Kn1ghtR1d3rOfD00m]

thank you Reza, 

I now start to understand. Yes, however, actually, the final set will be the Core multilayer ----> FW--->3850 stack----> Router ISR

so basically, when you say my config looks correct, are you referring only to the router portion? 

Cause the switch is a L2 port channel example, 

Thats where I get confused, if switch side should be Layer 3 or Layer 2, and in the Router ISR side, definitely should be Layer 3

[Reza Sharifi]

I apologize. I should have said that you also need an IP on the switch side. So, the Portchannel needs to have an IP on each side (layer-3).

example for the switch

interface port-channel1
ip address 10.10.10.2 255.255.255.0
exit

And one more thing, the switch side does not need to be a trunk port. Simply an access port

switch:

int gig1/0/2

channel-group 1 mode on
switchport mode access

switch port access vlan xx

exit

int gig2/0/2

channel-group 1 mode on
switchport mode access

switch port access vlan xx

exit

HTH

[Kn1ghtR1d3rOfD00m]

Got it, thank you so much for your response, let me try to make it and I will post how it went,