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I'm trying to configure a DHCPv6 server to provide more than one NTP address (option 56) using the isc-dhcpd server. Is there a currently supported way of doing this?

My first attempt was defining a custom option 56 in the configuration to be an array of ip addresses, however, I found that isc-dhclient that I use on the client side picks up only the first address, but then again, according to RFC 5908 the option must contain only one time source.

The RFC does, however, say that "This option can appear multiple times in a DHCPv6 message. Each instance of this option is to be considered by the NTP client or SNTP client as a server to include in its configuration." Following this, I tried to include my custom option 56 two times in the config file, but this time dhcpd sent only one of the options in the packet.

So that's what I want to know, is there currently a supported way to provide multiple NTP sources with isc-dhcpd and isc-dhclient for DHCPv6?

Thanks in advance!

vbeljan
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1 Answers1

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isc-dhcp-server allows you to override previous configured options, so if you set option 56 twice, it will only insert the later one. It doesn't violate the RFC but it does make configuring the server confusing if you're reading the RFC to do so.

The RFC is also a little confusing to read, the way I interpreted it based on the diagram is that it's a list of suboptions, and each suboption only contains one of 3 types (ip/fqdn/multicast).

"The option itself does not contain any value. Instead, it contains one or several suboptions that carry NTP server or SNTP server location. This option MUST include one, and only one, time source suboption."

Should read something like:

"The option itself does not contain any value. Instead, it contains one or several suboptions that carry NTP server or SNTP server locations. A suboption MUST include one, and only one, time source.

Jabrwock
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