ntp server




ntp server ip-address [version number] [key keyid] [source interface] [prefer]
no ntp server ip-address


Syntax Description:

ip-address IP address of the time server providing the clock synchronization.
version (Optional) Defines the NTP version number.
number (Optional) NTP version number (1 to 3).
key (Optional) Defines the authentication key.
keyid (Optional) Authentication key to use when sending packets to this peer.
source (Optional) Identifies the interface from which to pick the IP source address.
interface (Optional) Name of the interface from which to pick the IP source address.
prefer (Optional) Specifies that the server referenced in this command is preferred over other configured NTP servers.


Command Description:

To allow the software clock to be synchronized by a Network Time Protocol (NTP) time server, use the ntp server global configuration command. To disable this capability, use the no form of this command.

No peers are configured by default. If a peer is configured, the default NTP version number is 3, no authentication key is used, and the source IP address is taken from the outgoing interface.

Use this command if you want to allow the system to synchronize with the specified server. The server will not synchronize to this machine.

Use the prefer keyword if you use this command multiple times, and you want to set a preferred server. Using the prefer keyword reduces switching back and forth between servers.

If you are using the default version of 3 and NTP synchronization does not occur, try using NTP version 2. Some NTP servers on the Internet run version 2.


The following example configures a router to allow its software clock to be synchronized with the clock by the device at IP address using NTP version 2:

Router(config)# ntp server version 2



Related Commands:

ntp peer
ntp source

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