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Collaboration, Voice & AV · Advanced

Certificate Trust List (CTL)

A CUCM file of trusted server certificates that enables mixed mode for encrypted and authenticated phone signaling and media.

Definition

The CTL contains certificates for CallManager, TFTP, CAPF and security token signers and is downloaded and trusted by phones. Creating it switches the cluster to mixed mode, using hardware USB eTokens or the tokenless method with utils ctl set-cluster mixed-mode. Mixed mode is required for phones using authenticated or encrypted device security profiles with TLS and SRTP.

Example

utils ctl set-cluster mixed-mode enables mixed mode, after which phones can register with encrypted security profiles.

Exam tip

Mixed mode requires a CTL; Security by Default (ITL) alone does not encrypt signaling or media.

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