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All of your department’s IP phones are connected to the same Cisco Catalyst switch. The switch acts as a DHCP server for the voice VLAN. Another administrator power cycles the switch without warning. No calls are in progress.
Which of the following is most likely to occur?
- The IP phones will reset.
- The IP phones will disconnect but retain IP configuration information.
- The IP phones will disappear from the UCM configuration.
- The IP phones will not be affected by the power cycle.
Explanation:
Most likely, the IP phones will all reset when the administrator power cycles the switch. When an IP phone is disconnected from Cisco Unified Communications Manager (UCM), the phone will automatically reset in an attempt to reestablish communication. Therefore, if an IP phone suddenly resets or is continuously attempting to register with UCM, it is important to first verify the phone’s connectivity to the network switch.
The IP phones will disconnect but will not retain IP information. In this scenario, the IP phones receive their IP configurations from the Dynamic Host Configuration Protocol (DHCP) server that is running on the Cisco Catalyst switch that has been power cycled. When the IP phones reset, they will lose IP configuration information that was obtained from the DHCP server. Similarly, the IP phones will not be able to download configuration files from the Trivial File Transfer Protocol (TFTP) server until connectivity to the switch is restored.
The IP phones will not disappear from the UCM configuration. You can verify that an IP phone exists in the UCM by clicking Device > Phone > Find in UCM Administration and searching for the particular IP phone’s Media Access Control (MAC) address. The IP phone will no longer be registered with UCM when it loses connectivity. However, the IP phone’s record in the UCM configuration will remain there.
The IP phones will be affected by the power cycle. In addition to registration problems, IP configuration problems, and TFTP configuration problems, IP phones that are powered directly from the Cisco Catalyst switches by using Power over Ethernet (PoE) will not be able to receive power until the switch has restarted.
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