AP Behind A Router

I didn't see this in another post but forgive me if its a dup.

I would like to use an AP that is on a network that is connected to the "inside" network via a router. The network behind the router, has its own dhcp server.

Forgive the ascii art:

internet
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ASG/UTM
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Trusted internal network
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cisco router
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Trusted internal network 2
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AP30

How does the AP30 find the ASG/UTM to retrieve its configuration?