Configuring a Nexus NTP Server

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Best practice for a network environment is to have all devices synchronized with the same time. That way should you as the network administrator need to troubleshoot an issue, logs will be able to be accurately compared since the time stamps are directly comparable. When a Nexus device running the NX-OS is first installed, there are a few steps that are needed to configure the device as a Nexus NTP server.

To jump ahead, the final config will look something like this:


ntp master 2
ntp server 0.north-america.pool.ntp.org prefer
ntp server 1.north-america.pool.ntp.org
ntp server 2.north-america.pool.ntp.org
ntp server 3.north-america.pool.ntp.org
ntp source-interface Ethernet1/1

So what exactly does all of that mean? Step by step, here is what we have. The first line is “ntpĀ master stratum 2”. This is the main command that enables the Nexus device to act as a ntp server on the network. The stratum 2 at the end of the command identifies what type of ntp server it is. A stratum 1 device is a device linked directly to a reliable source of UTC time such as GPS. This CANNOT be a link over a network. A stratum 2 server is a server that it connected to a stratum 1 server over a network path. This is by far the most common of ntp server that is used in most network applications.

The next 4 lines that I have listed are defining which public ntpĀ servers I will use to sync my time with. These are the ntp sources that my Nexus device uses to become a stratum 2 ntp server. The first one has the option “prefer” after it to set it as the primary. Best practice would be obviously to use more than one server here in the event one fails.

Lastly, a user can set the source-interface for the ntp server. This is how the IP address of the server can be defined so the other network devices know what IP to connect to. Some of the options look like this:


N7K(config)# ntp source-interface ?
ethernet Ethernet IEEE 802.3z
loopback Loopback interface
mgmt Management interface
port-channel Port Channel interface

Most common would be to use a routed interface or a loopback interface with an IP that would not change.

Those are the basics of making a Cisco Nexus ntp server. Pretty basic configuration overall, but definitely beneficial in a network environment.,

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