Hi, 2009/9/22 MontyRee <chulmin2 at hotmail.com>: > I set 'server' directive like below at ntp.conf > > server 0.centos.pool.ntp.org > > if 0.centos.pool.ntp.org has multiple ip address 10.10.23.44 and 10.10.23.45, > and after some time 10.10.23.44 goes down, courrent configuration(10.10.23.44) > will be changed to 10.10.23.45 automatically or not without restarting ntpd? I don't think it does, that's why I think you should use multiple server directives with 0, 1, 2, ... names on them in case one of them fails. Although not stating this directly, this page seems to confirm that when it says "It can rarely happen that you are assigned the same timeserver twice - just restarting the ntp server usually solves this problem." http://www.pool.ntp.org/use.html You might find these pages interesting: http://www.eecis.udel.edu/~mills/ntp/html/manyopt.html http://www.eecis.udel.edu/~mills/ntp/html/assoc.html In particular, it seems that using the "pool" configuration option of NTP might do a smarter job. I never used it though, so I couldn't say... HTH, Filipe