Configuring System Information 111Polling for Anycast information is used when the server IP address is unknown. If this method isselected, all SNTP servers on the network can send synchronization information . The device issynchronized when it proactively requests synchronization information. The best response (loweststratum) from the first 3 SNTP servers to respond to a request for synchronization information isused to set the time value. Time levels T3 and T4 are used to determine the server time.Using Anycast polling to get time information for synchronizing device time is preferred to usingBroadcast polling to get time information. However, this method is less secure than unicast polling,because SNTP packets are accepted from SNTP servers that are not configured on the device.Broadcast information is used when the server IP address is unknown. When a Broadcast messageis sent from an SNTP server, the SNTP client listens to the message. If Broadcast polling is enabled,any synchronization information is accepted, even if it has not been requested by the device. Thisis the least secure method.The device retrieves synchronization information, either by actively requesting information or atevery poll interval. If Unicast, Anycast and Broadcast polling are enabled, the information isretrieved in this order:• Information from servers defined on the device is preferred. If Unicast polling is not enabledor if no servers are defined on the device, the device accepts time information from any SNTPserver that responds.• If more than one Unicast device responds, synchronization information is preferred from thedevice with the lowest stratum.• If the servers have the same stratum, synchronization information is accepted from the SNTPserver that responded first.MD5 (Message Digest 5) Authentication safeguards device synchronization paths to SNTP servers.MD5 is an algorithm that produces a 128-bit hash. MD5 is a variation of MD4, and increases MD4security. MD5 verifies the integrity of the communication, authenticates the origin of thecommunication.The SNTP page contains links to pages that allow network managers to configure SNTPparameters. To open the SNTP page, click System→SNTP in the tree view.Defining SNTP Global ParametersThe SNTP Global Settings page provides information for defining SNTP parameters.To open the SNTP Global Settings page, click System →SNTP→Global Settings in the tree view.
