Refer to the exhibit. In an environment SIP devices are registered to CUCM and H.323 devices to VCS. What would be required to enable these calls to setup correctly?

A presearch transform manipulates dial strings before search, and does not resolve protocol incompatibility between SIP and H.323.

Changing the domain of a SIP endpoint affects registration addressing but does not enable protocol translation between SIP and H.323.

Disabling SIP in the external zone would prevent SIP communication entirely, making calls less likely to succeed rather than enabling them.

Cisco VCS supports protocol interworking between SIP and H.323, but this feature must be explicitly enabled by setting the interworking mode to 'On'. Without this, VCS cannot bridge signaling between H.323-registered endpoints and SIP-registered endpoints on CUCM, causing call setup to fail.