We have a core switch 6500 with vlan 10 & vlan 20. Both vlans are set to auto-auto (speed/duplex). We noticed that when we connect a PC on vlan 10 & transfer a file say 1gb. The rate is between 30-40mb per sec, so it's fast enough. But when we connect to those port belonging to vlan 20, the rate is about between 4-6mb per sec. Thats a large diference!
checked all settings are same except of course for the ip, subnets....etc.
After we adjusted the the ports belonging to vlan 20 to Full-duplex, 1000Mb/s, the issue was resolved.
Any explanation on this?