Disabling NTP on an InterfaceBy default, NTP is enabled on all active interfaces. If you disable NTP on an interface, Dell Networking OS drops any NTP packets sent tothat interface.To disable NTP on an interface, use the following command.• Disable NTP on the interface.INTERFACE modentp disableTo view whether NTP is configured on the interface, use the show config command in INTERFACE mode. If ntp disable is notlisted in the show config command output, NTP is enabled. (The show config command displays only non-default configurationinformation.)Configuring a Source IP Address for NTP PacketsBy default, the source address of NTP packets is the IP address of the interface used to reach the network.You can configure one interface’s IP address include in all NTP packets.To configure an IP address as the source address of NTP packets, use the following command.• Configure a source IP address for NTP packets.CONFIGURATION modentp source interfaceEnter the following keywords and slot/port or number information:• For a 10-Gigabit Ethernet interface, enter the keyword TenGigabitEthernet then the stack/slot/port/subport information.• For a 25-Gigabit Ethernet interface, enter the keyword twentyFiveGigE then the stack/slot/port/subport information.• For a 40-Gigabit Ethernet interface, enter the keyword fortyGigE then the stack/slot/port[/subport] information.• For a 50-Gigabit Ethernet interface, enter the keyword fiftyGigE then the stack/slot/port/subport information.• For a 100-Gigabit Ethernet interface, enter the keyword hundredGigE then the stack/slot/port information.• For a Loopback interface, enter the keyword loopback then a number from 0 to 16383.• For a port channel interface, enter the keywords port-channel then a number.• For a VLAN interface, enter the keyword vlan then a number from 1 to 4094.To view the configuration, use the show running-config ntp command in EXEC privilege mode (refer to the example in ConfiguringNTP Authentication).Configuring NTP AuthenticationNTP authentication and the corresponding trusted key provide a reliable means of exchanging NTP packets with trusted time sources.NTP authentication begins when the first NTP packet is created following the configuration of keys. NTP authentication in Dell NetworkingOS uses the message digest 5 (MD5) algorithm and the key is embedded in the synchronization packet that is sent to an NTP time source.Dell Networking OS Behavior: Dell Networking OS uses an encryption algorithm to store the authentication key that is different fromprevious Dell Networking OS versions; Dell Networking OS uses data encryption standard (DES) encryption to store the key in the startup-config when you enter the ntp authentication-key command. Therefore, if your system boots with a startup-configuration from anDell Networking OS version in which you have configured ntp authentication-key, the system cannot correctly decrypt the keyand cannot authenticate the NTP packets. In this case, re-enter this command and save the running-config to the startup-config.System Time and Date 839
