ESX 4.1
I'm in the process of setting up a loadbalanced exchange cluster. I've 2 CAS servers, 1 Blackberry Enterprise Server and use a Virtual Appliance (loadbalaner.org) as the loadbalancer.
As soon as the BES uses the loadbalancer to connect to Exchange, problems come up with sending attachments from BB devices. Also Outlook clients hang at random moments when working with attachments.
I've been capturing network traffic with Wireshark and seeing a lot of [TCP dup acks].
While further investigating, I was doing a capture on the fileserver (als a VM) and there I saw the dup acks also once in a while (up to 40-50 dup acks to the same segment).
So I think we have a deeper network issue that showed up with the loadbalancer.
I've tryed several thing to no succes:
Put the VM on the same host
E1000 instead of VMXNET3
Fixed speed/duplex (1 GB Fault)
Create a local vSwitch (we use vDistributed switches)
For the Exchange servers change the RPC port to dynamic instead of static.
Some questions I have.
Can the physical layer play a part in this, even when staying on 1 host regarding the traffic?
What/where else to look?
