I have a client who I suspect has NBL Unicast port flooding going on and it is proving quite tricky to prove. My SQL queries are timing out immediately and I am getting NetLib errors (VB losing the network flow from what I can tell). Anyway, this client has 9 NLB servers plugged into an old CatOS Cisco core switch. There are 3 clusters, all using Unicast with 2 NICs. One NIC has the cluster VIP and a dedicated IP. The other NIC has a dedicated service console IP on the same subnet. Both NICs have default gateways.
From my experience, I have always been told that you don't put 2 DGs on the same subnet. You will get bad results when both try to register in DNS, when Client for MS Networks advertises the server, and when File and Print Sharing for MS advertises itself.
I need solid documentation explaining that this is bad and why. I have found this: http://download.microsoft.com/download/1/7/0/170690b4-87d2-402c-8ec9-6b76c5db4bdf/nlbbp.doc
But the instructions lack a degree of clarity. In the first doc, it tells you not to put 2 DGs on NICs of the same subnet but it is under the Windows 2000 heading, not the Server 2003 heading. There is room for interpretation here and I am looking for a rock-solid document.
The second link is a blog post and is not something I will walk into a client's site with and say "hah, I told you it wasn't set up properly".
I am hung up on a few things here:
-I think Unicast NLB is causing port flooding but cannot "show" this to them since they don't have the ability to monitor Unicast traffic on their core...I also cannot point out what levels of Unicast flooding would cause issues.
-I am pretty sure they should not be using a second NIC on the same subnet...and if they choose to do so, they should CERTAINLY not have 2 default gateways on the same subnet.
-I know they don't have any special configuration in their ARP routes or CAM tables but the document that tells me they need this is specific to Multicast NLB. This leads me to believe that Unicast NLB does not require this...
Can someone please point me to some definitive answers I can show this client? I have ~200 angry users and some frustrated techs who don't think they have a networking problem...I have ~500 other client sites using this software (minus the Unicast NLB) who are having no issues.
The only other clients I have who load balance TS (they don't like Citrix...) are using either hardware load balancing or Multicast IGMP NLB.