Final answer:
To configure an internal router as an NTP server with a stratum 5, use 'ntp master 5'. Then, configure other routers in the network to synchronize with it by using the 'ntp server IP_ADDRESS' command, substituting 'IP_ADDRESS' with the actual IP address of the internal NTP server.
Step-by-step explanation:
To configure an internal router as an authoritative NTP server with a stratum level of 5, and set up other routers to synchronize with it, you'll need to use a set of commands on the router designated as the NTP server. First, you have to specify the NTP master with a stratum level of 5. Second, you need to configure the rest of the routers to use this internal router as their NTP server.
Example Configuration on NTP Server Router:
It is critical to ensure that the NTP server router has the correct time and is synchronized with a reliable source before becoming the master clock for other devices on the network, as all of them will depend on its accuracy.