Uplinks on 3750 Stacks

Question

We are at the early stages in deploying a Campus LAN, at the access layer we are planning on using 3750 stacks with 2 x 2gb etherchannel uplinks going to diverse core switches; what is the best practice for the cross-stack etherchannel port assignment. E.g. Would it be best to put the first etherchannel uplink on the stack master and the second etherchannel on a non-master switch? Also what are the recommendations for using STP (R. PVST+) or load balancing in this scenario?

Answer 1

For cross-stack EtherChannel configurations, ensure that all ports targeted for the EtherChannel are either configured for LACP or are
manually configured to be in the channel group using the channel-group channel-group-number mode on interface configuration command. The PAgP protocol is not supported on cross- stack EtherChannels.
Here is the procedure from the 3750 12.2.25 docs.
This example shows how to configure a cross-stack EtherChannel. It
assigns two ports on stack member 2 and one port on stack member 3 to
channel 7 using LACP active mode:
Switch# configure terminal
Switch(config)# interface range gigabitethernet2/0/4 -5
Switch(config-if-range)# no ip address
Switch(config-if-range)# no switchport
Switch(config-if-range)# channel-group 7 mode active
Switch(config-if-range)# exit
Switch(config)# interface gigabitethernet3/0/3
Switch(config-if)# no ip address
Switch(config-if)# no switchport
Switch(config-if)# channel-group 7 mode active
Switch(config-if)# exit
check out the following link for more information on configuring Etherchannels :
http://www.cisco.com/en/US/customer/products/hw/switches/ps5023/products_configuration_guide_chapter09186a00801a658f.html#12539