One cool new feature of ESX 3.5 is their Cisco Discovery Protocol Support. CDP allows ESX to capture and broadcast Cisco related information to and from the switches. Information such as management IP addresses and switch ports. The type of information that is INVALUABLE when trying to explain to a network administrator that you need 4 of the 6 network cards coming out of your 1 ESX host set for VLAN trunking! For new 3.5 users, these features are ready to go right after installation. No additional configurations necessary.
What if it's not THERE?!?
For users who have upgraded from 3.x to 3.5, the CDP information is turned off by default.
To remedy the situation, putty into your ESX host and type esxcfg-vswitch –Bboth vSwitch[x]
Replace [x] with the number of your vswitches (0,1,2, etc). esxcfg-vswitch –l to list them out in case you are not sure.