Cisco 3850 Etherchannel issue

[pushkin.sawhney]

Hi All

I am trying to connect two Cisco 3850 stacks using EtherChannel but having issues as they seem to cause an error/failure on the EtherChannel (see attached image of test lab set-up), The stacks themselves are connected using StackWise cable and operational.

I am using two different ports (Gi1/0/48 and G2/0/48) from different switches in the stack to form Etherchannel link, the mode configured is ON/ON as recommended by Cisco and forum members.

Sw3 config:

!
interface GigabitEthernet1/0/47, Gi2/0/48
description #Inter-Switch PortChannel (Po1) Link#
switchport mode trunk
channel-group 1 mode on
end

Sw2 config:

!

interface GigabitEthernet1/0/47, Gi2/0/48
description #Inter-Switch PortChannel (Po1) Link#
switchport mode trunk
channel-group 1 mode on

end

One of the suggestions was to use the same ports from the same switches in Stack but that forms a single point of failure which is not acceptable.

Can you please review and let me know your recommendations?

Thanks in advance

[Seb Rupik]

Hi there,

I am surprised you have seen references specifying mode on as preferred.

I would suggest using mode active on both ends. Using LACP on the links will necessitate negotiation between the stacks and this will aid troubleshooting, as opposed to mode on which just turns on the taps and hopes for the best! :)

cheers,

Seb.

[pushkin.sawhney]

Thanks for the update Seb, I am going to try the following configuration on both switch stack side with LACP and confirm shortly:

interface GigabitEthernet1/0/47, Gi2/048
description #Inter-Switch PortChannel (Po1) Link#
switchport mode trunk
channel-group 1 mode active

[Joseph W. Doherty]

Like Seb, surprised you've seen references to using manual mode. Perhaps that was in reference to connecting to a small ISR? Otherwise, as already suggested by Seb, try using active (LACP) mode.

That said, how do you know the "manual" mode "failed"?