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A silly question probably, but guess I need to ask.

If I've got four centos boxes that are acting as ntpd multicast servers, will the multicast address configured in each box's ntp.conf all be the same (like 224.0.1.1) on all four boxes?

Or does each multicast address configured in ntp.conf need to be different, for example:

CentOS1    multicast    224.0.1.1

CentOS2    multicast    224.0.1.2

CentOS3    multicast    224.0.1.3

CentOS4    multicast    224.0.1.4

Thanks!

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up vote 3 down vote accepted

You should only use 224.0.1.1 under one of two conditions.

  • You are sure to only broadcast this address on your internal network. This means specifically firewalling this address from crossing all boundary points of your network.
  • Using symetric key encryption so that only clients with your symetric key will understand or reply to your time broadcasts.

For multicast configurations all the server can have the same address. You can configure them with different addresses if you really want, but unless you want to segment which clients get time from which server there's no real benefit.

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