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How do I activate NTP service?
Enable an NTP Service
- Install the ntp package:
- Edit the /etc/ntp.conf file to add NTP servers, as in the following example:
- Start the ntpd service:
- Configure the ntpd service to run at boot:
- Synchronize the system clock to the NTP server:
- Synchronize the hardware clock to the system clock:
What ports need to be open for NTP?
22.5. NTP is a UDP-based service. NTP servers use well-known port 123 to talk to each other and to NTP clients. NTP clients use random ports above 1023.
How can I tell if my UDP port 123 is open?
Follow below steps to check if UDP port is open or closed:
- Open a packet sniffer.
- Send a User Datagram Protocol (UDP) packet.
- After sending the UDP packet, if you receive ‘ICMP port unreachable’ message, then the UDP port is closed.
- If not, then the UDP port is open or something is blocking the ICMP.
Do you need to have your own NTP server?
For many types of applications having your own NTP server is unnecessary. For example, you do not need one if you want to use the protocol and can reliably access and synchronize with 3rd party NTP servers over the internet (more on those resources below).
How to configure NTP access restrictions global configuration?
♦ query-only—Allows only NTP control queries. ♦ serve-only—Allows only time requests. ♦ serve—Allows time requests and NTP control queries, but does not allow the switch to synchronize to the remote device. ♦ peer—Allows time requests and NTP control queries and allows the switch to synchronize to the remote device.
How to remove access control to NTP services?
To remove access control to the switch NTP services, use the no ntp access-group {query-only | serve-only | serve | peer} global configuration command. This example shows how to configure the switch to allow itself to synchronize to a peer from access list 99.
How does NTP provide an accurate time source?
NTP can provide an accurate time source through consensus with multiple input servers. It can also identify which available time servers are inaccurate. One challenge is that NTP was built during a time when the Internet community was friendlier.