I have setup, in a lab, an Exchange organization. I have:
2 HT/CAS servers
2 Mailbox servers
We have this setup in VMWare ESXi 4.0 with two hosts, each with one of each type of server. I have setup a CAS array, following all guidelines, using WNLB for the nlb cluster. From the HT/CAS servers, if I go into IE and type in the FQDN, it works. If I try from any other box in the organization, including a client machine we threw up, it doesn't work. From those boxes, I get a Destination host unreachable, trying to ping either the FQDN of the CAS array, or the nlb cluster IP address.
You may have to add a static ARP entry to the ARP table of the nearest Router or Layer-3 switch containing the MAC address of the VIP. This is most likely not an Exchange problem.
Microsoft Premier Field Engineer, Exchange
MCSA 2000/2003, CCNA
MCITP: Enterprise Messaging Administrator 2010
Former Microsoft MVP, Exchange Server
My posts are provided "AS IS" with no guarantees, no warranties, and they confer no rights.
On the HT/CAS servers, the Public profile of the Windows Firewall was on. Turned it off, with no change. No AV running on any of these machines, as it is a completely secluded area, just for this testing process.
If I go to the IP address of either of the node servers in the NLB cluster/CAS array, I get to OWA no problem. But if I go to the FQDN of the array, or the IP of the array, I get nothing.
On these HT/CAS servers, we have 2 NICs on each box. I had configured one NIC each to be the Network traffic, and one NIC to be the CAS array traffic. So, in the NLB cluster, I was using the CAS NICs. Only issue with this is that those NICs are currently connected with a crossover cable.
In troubleshooting, I deleted the hosts from the NLB cluster one at a time, and reentered them, using the Network NIC. Everything started working again. I'm able to connect to OWA from any machine in the lab.
Our next step is to run cables from the CAS NICs to the physical switch, and put the NLB cluster back to using the CAS NICs, and see what happens. I think it will work just fine.