PowerHA SystemMirror and NIM mksysb failures

I built a basic two-node PowerHA SystemMirror (HACMP) cluster for my team a little while ago to use as a test environment for patch updates. While it wasn’t a true reflection of how the production environment is configured, it was enough to test functionality. As such, I configured a single virtual ethernet adapter in each cluster node, which would house both the boot IP and the service IP of the cluster. After a couple of weeks, I noticed that my weekly NIM mksysb’s on one of the two cluster nodes was always failing. Further investigation found that the NIM mksysb’s would always fail on the cluster node that had the active resource group with the service IP attached to it. If I failed the resource group over to the other cluster node, the NIM mksysb would complete successfully.
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