Administrator Guide

Disabling NTP on an Interface
By default, NTP is enabled on all active interfaces. If you disable NTP on an interface, Dell Networking OS drops any NTP packets sent to
that interface.
To disable NTP on an interface, use the following command.
• Disable NTP on the interface.
INTERFACE mode
ntp disable
To view whether NTP is configured on the interface, use the show config command in INTERFACE mode. If ntp disable is not
listed in the show config command output, NTP is enabled. (The show config command displays only non-default configuration
information.)
Configuring a Source IP Address for NTP Packets
By 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 mode
ntp source interface
Enter the following keywords and slot/port or number information:
• For a 10-Gigabit Ethernet interface, enter the keyword TenGigabitEthernet then the slot/port[/subport] information.
• For a 40-Gigabit Ethernet interface, enter the keyword fortyGigE then the 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 Configuring
NTP Authentication
).
Configuring NTP Authentication
NTP 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
Networking OS 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 from
previous 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 an Dell Networking OS version in which you have configured
ntp authentication-key, the system cannot correctly decrypt
the key and 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
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