Assigning Static Ports to Netlogon and NTDS on Servers

[Will]

We assigned a static RPC port to the NTDS service in order to monitor
traffic through a firewall carefully. What we are noticing is that when a
user logs in, the netlogon service is now also using the same static port.
Does Netlogon just inherit whatever RPC port is used by NTDS?

To assign NTDS a static port, you use registry key:

HKLM\CurrentControlSet\Services\NTDS\Paramaters\TCP/IP Port

I was *not* able to successfully use the same strategy to assign a different
static port to Netlogon. We tried:

HKLM\CurrentControlSet\Services\Netlogon\Paramaters\TCP/IP Port

with a different TCP port number, but this registry setting appears to get
ignored. Instead, Netlogon service uses the TCP port defined as above for
NTDS.

Can someone explain that result?