How to fix common Network Load Balancing issues

[EricTheRed]

The following are the general steps that one may want to try while troubleshooting common NLB (WLBS) issues like:

1) Nodes not converging.
2) Adding a node to the NLB cluster stops the cluster from working.
3) Unable to access NLB from another VLAN.
4) NLB not working properly.

1) First collect the "WLBS Display" logs from all the nodes. Compare them for any mismatching rule or Parameter. Try to find if you see frequent convergence happening. If you see lot of convergence happening but nodes never getting converged then you might want to check the heart beat communication.
If you find an error message like "cluster Mode Stopped" then again you might want to check the heart beat communication as well as for any misconfiguration in the NICs. Also make sure that your NICs drivers are updated and you don't have teaming enabled on the nodes. Teaming causes lot of such issue. Moreover NLB cluster is not recommended with teaming enabled on the nodes.

2) Try to ping the VIP from the same V/LAN. Are you able to ping it? If yes then try to ping the VIP from different VLAN. If you are not able to ping the VIP from there then check the ARP table entry cached i the router/switch between the two VLANs. If you find that you are not able to ping the VIPs from either of the VLAN then go ahead and connect the Nodes to a hub. Now try to ping the VIPs. Are you able to do so? If yes you know where the problem is and if no then also you know where the problem is.

3) Try to ping the DIP of the nodes you should be able to do so. If not then you know where the problem is.

Make sure that you always use the layer two switches while using WLBS. Also recheck the configuration to find out if there is any mismatch. Make sure you break the teaming before you do any troubleshooting. Never use cross cable to connect the nodes for private (heart beat) communication. Make sure you NIC drivers are updated to the latest version.

If these steps doesn't prove helpful in identifying the issue then you may want to contact Microsoft support to resolve your issue.

[Charth]

The steps mentioned by EricTheRed are really helpful to me and I have also used them to get rid of the problem that I was facing and was also able to solved it cleanly without any setbacks.