[Webinar] Streamline your web hosting managementRegister Today

  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 432
  • Last Modified:

NLB Servers cannot communicate with each other


I'm having trouble setting up a NLB cluster - my setup

The network of 60+ clients lives on IPs 10.1.2.x
The servers (AD, DNS, DHCP, DFS-R  etc) live on IPs 10.1.1.x
Subnet mask on both clients and servers is
Gateway is

2 windows 2003 servers, (call them A and B) each had 1 network card - A is and B is
A and B are file severs hosting DFS-R shares (replicated with each other)
A is also the Print server for the network.

I installed an additional network card into each server and began to configure each server using the NLB snap-in.

I configured A such that card 1 was untouched (,,
and card 2 is (,, no gateway) added to a new unicast NLB cluster called "cluster" on

I added DNS records such that points to cluster - from domain PCs and server B  I can ping A, and ping cluster OK using both hostnames and IP addresses.

So far so good...

On B I configure the 2nd card as,, no gateway.

Back on A I right click the cluster in the NLB manager, put B in the host box and choose the 2nd card  (the card). I left the priority at 2, and clicked finish.

After a few moments B is shown as pending and then unreachable - now the problems start -  I cannot ping B from A via ip address or dns name. B cannot ping A via IP or DNS.
When I ping A from A using hostname, it replies on the 192.168 interface, not the 10.1 interface

I can open the NLB management snap-in on each server, and it will show that that server is part of the cluster, but the other server is unreachable.

Any help will be appreciated


1 Solution
"I can open the NLB management snap-in on each server, and it will show that that server is part of the cluster, but the other server is unreachable."
That's the way it works. I've always used NLB manager from a different server.
How To Configure Network Load Balancing Parameters in Windows Server 2003
How To Set Up TCP/IP for Network Load Balancing in Windows Server 2003
How-To: Configure Network Load Balancing (NLB) with Two Network Adapters

I think the last link should interest you the most :-)
M_A_D_C_A_TAuthor Commented:

I followed those notes from the last link you poseted, but I had the same trouble the first few people to comment on the post had.

I have resolved the issue by assigning both NICs on each server IP addresses in the 10.1 space. I have also set it up as a Multicast cluster. Now each server can still replicate DFS shares, and the cluster works properly. If I disconnect one  of the  NICs in the NLB cluster, the other takes over; If i disconnect both, the cluster is unreachable.
Jim P.Commented:
The way we always did it was to have VLAN (or preferably a second switch) to handle the back-channel 196. while the 10. went out the main switch.

Featured Post

Free tool for managing users' photos in Office 365

Easily upload multiple users’ photos to Office 365. Manage them with an intuitive GUI and use handy built-in cropping and resizing options. Link photos with users based on Azure AD attributes. Free tool!

Tackle projects and never again get stuck behind a technical roadblock.
Join Now