Filter hooks help to direct traffic in a Network Load Balancing (NLB) cluster by filtering network packets. If the filter hooks are not properly configured, the NLB cluster will continue to converge and operate normally, however, the server application that is running with NLB will not be able to properly register the hooks.
Ensure that the NLB filter hooks are properly registered
You should check with the server application running with Network Load Balancing (NLB), such as ISA Server, and make sure that the NLB hooks are being properly registered. You can re-attempt the registration operation using the workload management utilities.