Troubleshooting networking is rather difficult if you can only connect to your ESX box via the console. Luckily I came across the instructions below

1. Log in into ESX 3.5 via SSH as root.
2. Run the following command on ESX command line :

   > vmware-vim-cmd hostsvc/net/query_networkhint

3. The following information is displayed:

• Virtual switch port information
• CDP information from the physical Cisco switch connecting to the ESX host .

Here is the link to the VMware KB Article. 

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1007069