Switch Management Commands 1845Clock CommandsReal-time ClockThe Dell EMC Networking supports a real-time clock that maintains thesystem time across reboots. The system time is used to timestamp messagesin the logging subsystem as well as for the application of time based ACLs.The administrator has the ability to configure and view the current time, timezone, and summer time settings.The earliest date that can be configured is Jan 1, 2010.Simple Network Time ProtocolThe Simple Network Time Protocol (SNTP) is widely used for synchronizingnetwork resources. SNTP Version 4 is described in RFC 2030. SNTP is anadaptation of the Network Time Protocol (RFC 1305) useful for situationswhere the full performance of NTP is not justified. SNTP can operate inunicast mode (point-to-point) or broadcast mode (point-to-multipoint).Various NTP implementations can operate as either a client or a server. To anNTP or SNTP server, NTP and SNTP clients are indistinguishable. Likewise,to an NTP or SNTP client, NTP and SNTP servers are indistinguishable.Furthermore, any version of NTP is compatible with any other version of NTP.Dell EMC Networking SNTP implements the client side of SNTP.Support for IPv6 address configuration is provided to the existing SNTPclient. The end user can configure either an IPv4 or IPv6 address or a hostname for an SNTP server among the list of servers. In unicast mode, one ofthe servers from the list is selected as the active server to be used for pollingbased on priority and configured order. The servers are treated alikeindependent of IPv4 or IPv6 or hostname address formats. At any given pointof time, the client operates in unicast or broadcast mode. In broadcast mode,SNTP client listens on the well known multicast group address 224.0.1.1(reserved for NTP) for server packets from IPv4 networks on port number 123.On IPv6 networks, the SNTP client listens to the link-local scoped IANAmulticast address ff02::101 (reserved for SNTP) for server packets on portnumber 123. The client logic to handle packet contents doesn’t change withsupport for IPv6 networks.
