External Devices - Cisco 9971 Administration Manual

8 Request the ITL file. The phone requests the ITL file after it requests the CTL file. The ITL file contains
the certificates of the entities that the phone can trust. The certificates are used to authenticate a secure
connection with the servers or to authenticate a digital signature signed by the servers. Cisco Unified
Communications Manager 8.5 and later supports the ITL file.
9 Access a TFTP server. In addition to assigning an IP address, the DHCP server directs the
Cisco Unified IP Phone to a TFTP Server. If the phone has a statically defined IP address, you must
configure the TFTP server locally on the phone; the phone then contacts the TFTP server directly.
You can also assign an alternate TFTP server to use instead of the one that DHCP assigns.
Note
10 Request the configuration file. The TFTP server has configuration files, which define parameters for
connecting to Cisco Unified Communications Manager and other information for the phone.
11 Contact Cisco Unified Communications Manager. The configuration file defines how the Cisco
Unified IP Phone communicates with Cisco Unified CM and provides a phone with the load ID. After it
obtains the file from the TFTP server, the phone attempts to make a connection to the highest priority
Cisco Unified CM on the list.
If the security profile of the phone is configured for secure signaling (encrypted or authenticated) and the
Cisco Unified Communications Manager is set to secure mode, the phone makes a TLS connection.
Otherwise, the phone makes a nonsecure TCP connection.
If the phone was manually added to the database, Cisco Unified Communications Manager identifies the
phone. If the phone was not manually added to the database and autoregistration is enabled in Cisco
Unified Communications Manager, the phone attempts to autoregister itself in the Cisco
Unified Communications Manager database.
Autoregistration is disabled when you configure the CTL client. In this case, you must add the phone to
Note
the Cisco Unified Communications Manager database manually.

External Devices

We recommend that you use good-quality external devices that are shielded against unwanted radio frequency
(RF) and audio frequency (AF) signals. External devices include headsets, cables, and connectors.
Depending on the quality of these devices and their proximity to other devices, such as mobile phones or
two-way radios, some audio noise may still occur. In these cases, we recommend that you take one or more
of these actions:
• Move the external device away from the source of the RF or AF signals.
• Route the external device cables away from the source of the RF or AF signals.
• Use shielded cables for the external device, or use cables with a better shield and connector.
• Shorten the length of the external device cable.
• Apply ferrites or other such devices on the cables for the external device.
Cisco cannot guarantee the performance of external devices, cables, and connectors.
Cisco Unified IP Phone 8961, 9951, and 9971 Administration Guide for Cisco Unified Communications Manager 10.0
External Devices
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