[c-nsp] Weird Port Loopback Issues with 3750 and ESX 3.5

[Justin Shore]

aaron wrote:
> I am hoping some of you out there may have experienced this problem in the
> past. We have a spare NIC on a DELL X445 (Broadcom  NetXtreme BCM5793
> 1000Base-T) running ESX 3.5. No matter what I do I cannot seem to get this
> NIC working properly. I have it connected to a 3750 switch GIG GLC-T SFP
> port and I am getting err-disable loopback issues where the switch is
> actually receiving its own keep alives on the same port. 

What's being logged in the buffer when the port gets disabled?  I hate 
to ask the obvious but this isn't a STP issue, is it?  Is the ESX box 
configured with an internal switch that's passing BPDUs received on one 
interface back out the other, causing the port to go into blocking 
and/or becoming err-disabled thanks to bpduguard?

What are the other ports in the Dell configured like in VMWare?  How 
have you configured the problematic port in the 3750?  Do you have any 
VLANs overlapping between 2 of the ESX box's ports?  That will be a L2 
loop if the ESX box is configured with an internal switch that doesn't 
participate in STP.

Shooting from the hip but that's all I'm worth on a Friday afternoon.

Justin