HP Cisco MDS 9124 Cisco MDS 9000 Family CLI Configuration Guide, Release 3.x ( - Page 175

Chapter 5 Initial Configuration NTP Configuration Send documentation comments to [email protected] If you want to configure daylight savings time on multiple switches simultaneously, see the RUN CLI command feature in the Cisco MDS 9000 Family Fabric Manager Configuration Guide. NTP Configuration A Network Time Protocol (NTP) server provides a precise time source (radio clock or atomic clock) to synchronize the system clocks of network devices. NTP is transported over User Datagram Protocol UDP/IP. All NTP communications use Universal Time Coordinated (UTC). An NTP server receives its time from a reference time source, such as a radio clock or atomic clock, attached to the time. NTP distributes this time across the network. This section includes the following sections: • About NTP, page 5-19 • NTP Configuration Guidelines, page 5-19 • Configuring NTP, page 5-20 • NTP CFS Distribution, page 5-23 About NTP 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 happens 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 synchronization requests. By configuring an IP address as a peer, the switch 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 these instances point to different time servers, your NTP service is more reliable. Thus, even if the active server link is lost, you can still maintain the right time due to the presence of the peer. Tip If an active server fails, a configured peer helps in providing the NTP time. Provide a direct NTP server association and configure a peer to ensure backup support if the active server fails. If you only configure a peer, the most accurate peer takes on the role of the NTP server and the other peer(s) acts as a peer(s). Both machines end at the right time if they have the right time source or if they point to the right NTP source. NTP Configuration Guidelines The following guidelines apply to all NTP configurations: • You should have a peer association with another switch only when you are sure that your clock is reliable (which means that you are a client of a reliable NTP server). OL-16184-01, Cisco MDS SAN-OS Release 3.x Cisco MDS 9000 Family CLI Configuration Guide 5-19