In a large enterprise network, having one time standard for all
network devices is critical for management reporting and event logging
functions when trying to correlate interacting events logged across multiple
devices. Many enterprise customers with extremely mission-critical networks
maintain their own stratum-1 NTP source.
Time synchronization occurs when several frames are exchanged between
clients and servers. The switches in client mode know the address of one or
more NTP servers. The servers act as the time source and receive client
By configuring an IP address as a peer, the Cisco NX-OS device will
obtain and provide time as required. The peer is capable of providing time on
its own and is capable of having a server configured. If both of these
instances point to different time servers, your NTP service is more reliable.
Even if the active server link is lost, you can still maintain the correct time
due to the presence of the peer.
If an active server fails, a configured peer helps in providing the
NTP time. To ensure backup support if the active server fails, provide a direct
NTP server association and configure a peer.
If you only configure a peer, the most accurate peer takes on the role
of the NTP server and the other peer acts as a peer. Both devices end at the
correct time if they have the correct time source or if they point to the
correct NTP source.
Figure 1. NTP Peer and Server Association. Not even a server down time will affect well-configured switches
in the network. This figure displays a network with two NTP stratum 2 servers
and two switches.
In this configuration, the switches were configured as follows:
Switch-1 IPv4 address-10.10.10.1
Switch-1 NTP configuration
NTP server 10.10.10.10
NTP peer 10.10.10.2
Switch-2 IPv4 address-10.10.10.2
Switch-2 NTP configuration
NTP server 10.10.10.9
NTP peer 10.10.10.1