This is using 3 pcs of Cisco catalyst switch 3850-48, forms a stack. A Cisco Catalyst switch 3750 with sfp ports are used as core switch. However, when I tried to form a trunk between 3850 stack and 3750, I failed. Please help to show the correct way to form the trunk in steps. I found some forums state that you have to use etherchannel on top of the trunk, is this true?
thanks in advance.