In many cases we would require higher bandwidth within the organization while we have 1GB uplinks, or we stack switches and want to have multiple uplinks from each switch, or just to keep redundant link that is unblocked by STP. All these are simple scenarios that we face and the solution is rather simple.
Port Aggregation is the answer. Cisco calls it Etherchannel. Before configuring etherchannel, the ports taking part in this channel should have the following unified:
3-Spanning tree settings
4-access in same vlan
5-if trunk, then native vlan should be same. and should pass the same vlans.
6-all ports should belong to the same ether channel group.
There are besically two protocols to negotiate portchannels, LACP and PAgP. I would prefer to just turn the channel on without negotiating.
switch(config)# int range gig 0/1 – 4
switch(config-if)# channel-group 1 on
do the same configuration at the other side.