A SIP endpoint attempts to register with a Cisco VCS by using an alias that has previously been registered from
another IP address.
Which of the following will occur if the Cisco VCS is configured with the default settings?

A.
The VCS will deny the new registration and maintain the old registration.

B.
The VCS will deny the new registration and remove the old registration.

C.
The VCS will replace the old registration with the new registration.

D.
The VCS will allow the new registration while maintaining the old registration.

Explanation:
The Cisco TelePresence Video Communication Server (VCS) will allow the new registration while maintaining
the old registration. A Session Initiation Protocol (SIP) endpoint can always register an alias that is already in
use. When a call is placed to the alias, all endpoints that are registered with that alias will ring simultaneously.
When a SIP endpoint registers with the VCS, it will send its IP address and its Address of Record (AOR).
The AOR is used as the SIP alias and should be in the form of a Uniform Resource Identifier (URI). The Cisco
VCS acts as the SIP server and as a SIP registrar. The SIP registrar accepts registrations only for the domain
or domains for which it is authoritative. It can also proxy registration requests to another SIP registrar if it is
configured to do so.
The SIP endpoint needs to be able to discover the SIP registrar. If the endpoint is set for automatic SIP server
discovery, the endpoint will send a REGISTER message to the SIP server that is authoritative for the endpoint’s
domain. If the endpoint is set for manual SIP server discovery, the endpoint must be configured with the IP
address or the fully qualified domain name (FQDN) of the SIP registrar.Unlike SIP aliases, H.323 aliases must be unique. 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 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. However, you can configure the VCS to overwrite the old registration
with the new registration. Overwriting is useful for networks in which endpoints change IP addresses frequently.

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
SIP (PDF)
Cisco: Cisco TelePresence Video Communication Server, Administrator Guide, Software version: X8.1:
Configuring SIP (PDF)