Despite what your site's network staff have said, this is likely to be their issue.
If you are connecting to a managed switch, that entire peripheral may have specific settings on some or all of its ports.
I suggest you let that switch do whatever it expects to do and remove all customizations to your NIC's configuration. Let it auto-negotiate.
You should also ignore that link you have in your initial post. The ERI network interface that is described there was a very specific network chipset and used on a very small specific number of Sun SPARC boxes. It was known to have issues with proper negotiation (it would usually work but sometimes just get mucked up).
See this Symantec link http://www.symantec.com/business/support/index?page=content&id=TECH37566
and the following two Oracle notes: