Which of the following statements is correct regarding H.323 registrations on a Cisco VCS that is configured
with the default settings?

A.
H.323 endpoints cannot register to a Cisco VCS by default.

B.
H.323 endpoints must register manually by connecting to the IPv4 address of the Cisco VCS.

C.
H.323 endpoints must register automatically by sending out a Gatekeeper Discovery Request.

D.
H.323 endpoints can register manually by connecting to the IPv4 address of the Cisco VCS or automatically
by sending out a Gatekeeper Discovery Request.

Explanation:
By default, H.323 endpoints can register manually by connecting to the IPv4 address of the Cisco
TelePresence Video Communication Server (VCS) or automatically by sending out a Gatekeeper DiscoveryRequest. Cisco VCS is configured by default to be an H.323 gatekeeper. In order for a Cisco VCS to be an
H.323 gatekeeper, the H.323 mode must be enabled. To enable H.323 mode, navigate to Configuration >
Protocols > H.323 and set the H.323 mode option to On.
Manual registrations require that the H.323 endpoint be configured with the IPv4 address of the Cisco VCS and
be configured with an IPv4 address, subnet mask, and default gateway that will allow the endpoint to
communicate with the Cisco VCS. H.323 endpoints can register manually as long as the VCS is configured to
be an H.323 gatekeeper.
Automatic registrations require that the VCS be configured to allow automatic discovery. To enable automatic
discovery, navigate to Configuration > Protocols > H.323 and set the Auto discovery option to On. Automatic
discovery is enabled on Cisco VCS by default.
When an H.323 endpoint registers with Cisco VCS, the endpoint sends one or more of the following aliases to
the VCS:
One or more H.323 IDs
One or more E.164 aliases
One or more Uniform Resource Identifiers (URIs)
If an endpoint attempts to register an alias that has previously been registered from another IP address, the
VCS will reject the registration by default. You can configure Cisco VCS to overwrite the original registration by
navigating to Configuration > Protocols > H.323 and setting the Registration conflict mode option to Overwrite.

Cisco: Cisco TelePresence Video Communication Server, Administrator Guide, Software version: X8.1:
Registering aliases (PDF)
Cisco: Cisco TelePresence Video Communication Server, Administrator Guide, Software version: X8.1: About
H.323 (PDF)
Cisco: Cisco TelePresence Video Communication Server, Administrator Guide, Software version: X8.1:
Configuring H.323 (PDF)