The Dell PowerConnect 5548 switch with firmware 126.96.36.199 does not work with auto negotiate enabled on some Mac and other NICs.
The issue seems to be with the support for Green Ethernet. Here is the fix that worked for me:
5548-SW01(config)# no eee enable
As soon as commiting the change, the interface for the Mac systems came online.
The Mac ethernet ports need to be set to manual in order to access the switch without making the “no eee enable” config change.Read More...