The correct command to configure the new router to use 192.168.1.110 as its primary time source without the new router attempting to offer time to existing devices is ntp server 192.168.1.110 key 1 prefer. This command specifies that the new router will act as an NTP client and synchronize its time with the NTP server at
192.168.1.110, using the authentication key 1 and giving preference to this server over other possible servers.
The prefer keyword indicates that this server is preferred over other servers with the same stratum number.
The ntp server command is different from the ntp peer command, which configures the new router to act as an NTP peer and exchange time information with another NTP device. A peer relationship is bidirectional and symmetric, meaning that both devices can provide and receive time information from each other. A client-server relationship is unidirectional and asymmetric, meaning that the client only receives time information from the server and does not provide any time information to the server. Therefore, the ntp peer command is not suitable for the scenario, as it would make the new router attempt to offer time to existing devices, which is not desired. The primary keyword is not a valid option for either the ntp server or the ntp peer command, and it would cause a syntax error. References :=
* Implementing and Operating Cisco Security Core Technologies (SCOR) v1.0, Module 1: Security Concepts, Lesson 1.3: Network Time Protocol
* Configuring NTP - Cisco, Configuring NTP on the Switch, Configuring NTP in Client Mode
* NTP Commands - Cisco, ntp server, ntp peer