Windows Network Load Balancer issue

[JordanCN]

I have seen a couple of posts back in 2018 about issues with Windows NLB and the Meraki switches but I wanted to check in to see if a solution has been developed in the last 5 years.

My configuration is 2 Hyper-V servers both running Windows 2022 Std with about 5 VMS on each host.  I have 2 VMs where I want to use Windows NLB.  The two VMS are Windows 2022 Std VM setup on different hosts.  NLB on the two VMS is in IGMP Multicast mode (Tried Uni and just Multi with same results).  Both VMs configs have MAC Spoofing enabled for the NLB NIC.  Both physical NICs from each Hyper-V hosts are plugged into the same MS120-48.

Server1 - 192.168.1.10 (on Host 1)

Server1 - 192.168.1.20 (on Host 2)

NLB - 192.168.1.30

All the VMs on each Hyper-V host are able to connect (and ping) the NLB at 192.168.1.30.  No physical computers on the MS120 or other switch are able to connect or ping the NLB.  I am assuming the VMs on each host can only see the NLB node on their own server.

MS120 cannot ping the NLB and when I try to packet captuer for the NLB IP or MAC I just seen ARP requests with no response.

I have been seeing that in order to use Windows NLB I need to have a static entry for the virtual IP and MAC, but can't see how to get this on the Meraki.

[alemabrahao · Accepted solution]

The issue you’re experiencing, where the NLB is not reachable from physical computers on the MS120 or other switches, is a known issue.

The problem often arises due to how NLB responds to ARP requests, which can cause issues with the MAC address tables on physical switches. This is particularly true in Multicast mode, which you’re using.

One common solution is to use Unicast mode with a dedicated VLAN. This can help manage network traffic and prevent flooding. However, this might not be feasible in all network environments.

As for adding a static entry for the virtual IP and MAC on the Meraki, unfortunately, Meraki switches do not currently support adding static ARP entries. This is a limitation of the Meraki platform.

A workaround suggested in the community is to use Unicast NLB in a dedicated VLAN. This has been reported to resolve similar issues.

For more detailed guidance and potential workarounds, I would recommend reaching out to Meraki support.

[JordanCN]

Thanks for the info.  Is there another load blancer that is compatible with Meraki?

I am trying to setup 2 web servers that are running the same application.  I wanted to use the build in NLB so it wouldn't look sloppy by having 2 links to the web application incase one of the servers was under maintenance or the physical host for that server was offline.

I know I could put in another VM for a load balancer, but then that adds a third VM and my goal is to keep as few VMS as possible.