I got an interesting question about Proxy Controllers. The question was, if you have an asset on a network and two Proxy Controllers can access that network, can you control which Proxy Controller manages the asset?
Well, you do have some control, but before I get into that, it's worth noting that the Proxy Controller-Agent communication works differently in 12c than it did in prior versions of Ops Center. In older versions, an Agent was associated with one specific Proxy Controller, and if the Proxy Controller failed the asset's connection to Ops Center was broken. In 12c, if a Proxy Controller fails, you can migrate the assets to any other Proxy Controller with access to their network, keeping the assets managed.
So, in 12c assets are not as strongly tied to specific Proxy Controllers. When you try to discover an asset, Ops Center looks at which Proxy Controllers can access the asset, and picks the one with the least load.
However, you do have some options for controlling what asset goes to what Proxy Controller. First, you can put a Proxy Controller into maintenance mode by selecting the Proxy Controller and clicking Put in Maintenance Mode; this doesn't stop it from managing its existing assets, but it stops it from taking on new ones.
You can also set different power levels for your Proxy Controllers. Select the Enterprise Controller's Configuration tab, then select the Proxy Management subsystem. If you want Proxy Controller A to do twice the work as Proxy Controller B, for instance, set A's relative power to 2 and B's to 1.
The Feature Reference Guide goes into more detail about discovery, and the Administration Guide gives you more information about Enterprise Controller settings and asset migration.