The system clock starts at the beginning of every system startup keeping of the current date and time. The system clock keeps track of time internally based on UTC, also known as Greenwich Mean (GMT). Local time zone and daylight savings time must be configured to reflect the correct time relative to the local time zone.
Note
On the high-end routers such as the 7500 and 12000 Series, the system keeps time on an internal clock, thus time is not
lost during a reboot.
NTP is designed to synchronize the time on the device clock. An NTP network usually gets its time from an authoritative time
source, such as a radio clock or an atomic clock attached to a time server.
NTP is essential for syslog messages, and for troubleshooting and correlation activities. NTP uses UDP port 123 as both the
source and destination and can be secured using an authentication mechanism that uses the MD5 algorithm. The ntp command
from the global configuration mode can be used for all NTP-related configurations in the Cisco IOS.
Simple Network Management Protocol (SNMP)
SNMP is a widely used management protocol and defined set of standards for communication with devices connected to a TCP/network that are defined by the Internet Engineering Task Force (IETF).
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