Well as it turn’s out changing a node’s IP address in clustered environments doesn’t go that smoothly as one would expect. Not only that, F5 have made a annoyingly complex procedure of something that simple as changing one back end servers IP address. What I mean by that is, that in order to change the IP address of a node you actually have to delete the node and then re-create it. But when you have one node running a ton of services on different ports and is a part of a large amount of resource pools, etc you have to remove it from all of the resource pools before you can delete it. And then after creating the node again you have have to put it back in the pools you need it to be in.
As it turns out in a clustered environment when you do the aforementioned procedure and then try to sync the cluster member settings manually it will fail with an error message saying something like this:
0107003c:3: Invalid pool member modification. An IP address change from (192.168.1.1) to (192.168.1.2) is not supported.
So in order to avoid that error you need to sync the devices after you have finished all the deletion steps of the node and after you have done the config sync you may proceed with the creation of the node on the new IP address.
If you are already in the state where it is refusing to sync, well what helps is deleting the troublesome node on the secondary device also and then performing the config sync.