4.2.4 Specify Reliable KeyYou must specify a key to be a reliable one before it can be used for authentication.For example, if two routers want to use keyid 1 for authentication, both of them mustspecify it to be a reliable one.Perform the following configuration in system view.Table 4-9 Specify a key to be a reliable keyOperation CommandSpecify a key to be areliable keyntp-service reliable authentication-keyid key-numberRemove a reliable key undo ntp-service reliable authentication-keyid key-numberThe argument key-number is in the range of 1 to 4294967295.4.2.5 Specify a Local Interface for Sending NTP MessagesThis task specifies an interface whose IP address will be used as the source IPaddress carried in all the NTP messages sent from the local router to the time server.Perform the following configuration in system view.Table 4-10 Set a local interface for sending NTP messagesOperation CommandSet a local interface for sending NTPmessagesntp-service source-interface { interface-name |interface-type interface-number }Disable the interface as the interface forsending NTP messagesundo ntp-service source-interfaceYou can specify an interface by specifying its interface-name or interface-typeinterface number. The router will use the IP address of the interface as the source IPaddress carried by the NTP messages sent to the time server. The outgoing interfacespecified using the command ntp-service unicast-server or ntp-serviceunicast-peer, if there is any, will be preferred in case there is any difference.4.2.6 Set NTP Master ClockThis task specifies an external reference clock or the local clock as the NTP masterclock.Perform the following configuration in system view.3Com Router Configuration Guide Addendum for V1.2048