Hello friends, i am actually trying to do this same thing right now between a Cisco 2960 and a Summit x450x-48t. The Cisco Config side looks like this :
interface Port-channel1
description Trunk to Eng Extreme Switch
switchport trunk allowed vlan 113,560,561
switchport mode trunk
interface FastEthernet0/47
description Trunk to Eng Extreme Switch
switchport trunk allowed vlan 113,560,561
switchport mode trunk
shutdown
channel-group 1 mode active
interface FastEthernet0/48
description Trunk to Eng Extreme Switch
switchport trunk allowed vlan 113,560,561
switchport mode trunk
shutdown
channel-group 1 mode active
I need to connect ports 47,48 to the trunk etherchannel on the Cisco. then i will have ports on the extreme assigned to the 3 vlans as i need them.