| After years of working with Cisco switches, 90% of non-hardware related problems with L2 switches can be solved by doing one of the following things: 1)Power-cycle that sucker!
2)Verify speed and duplex settings are correct
3) Clear the arp cache
4)Make sure it hasn't re-set itself to it's default configuration.
5)Ensure that spanning-tree hasn't put the port into a blocking state.
6)Make sure that you have a good patch cord and it is all the way plugged in. If those don't do it, it's probably time to find yourself a guru. One other problem that the L2 switches have (especially the 29xx and 35xx switches) is that often the NIC on the host will initialize before the entire spanning-tree algorithm is run. Adding the command spanning-tree portfast to the interface will fix this. Just make sure that the ports it is enabled on is a host node and doesn't connect to another switch. | 
