-2

I am capturing DHCP packets with tcpdump. The client sends a DHCP request asking for the DHCP configuration which contains a request for NTP servers but in the DHCP ACK message sent by the router there is no NTP server information. Shouldn't the server answer with the NTP server's IPs as it does with the domain name servers? What am I missing?

I attatch screen shots of the request and ack messages

tcpdump command used: 

tcpdump -i eth0 -n port 67 and port 68 -w capture.pcap -v

DHCP REQUEST:

DHCP Request message

DHCP ACK:

Information received from the server in DHCP Acknowledge message

jap jap
  • 320
  • 2
  • 15
  • Which DHCP server are you using? Why _should_ it include NTP servers? Does it even know about NTP servers? – Roger Lipscombe Jul 03 '18 at 12:26
  • 2
    Stack Overflow is a site for programming and development questions. This question appears to be off-topic because it is not about programming or development. See [What topics can I ask about here](http://stackoverflow.com/help/on-topic) in the Help Center. Perhaps [Super User](http://superuser.com/) or [Unix & Linux Stack Exchange](http://unix.stackexchange.com/) would be a better place to ask. – jww Jul 03 '18 at 12:58
  • Sorry @jww , I wasn't aware of that. I placed the question in Linux Stack Exchange – jap jap Jul 03 '18 at 13:34
  • I'm voting to close this question as off-topic because this is a Linux operating system question and not a programming question. In addition, it is duped on https://unix.stackexchange.com/ – Rob Aug 28 '19 at 11:28

1 Answers1

-1

It depends on whether the DHCP server was configured to provide an NTP server. DHCP doesn't have to provide NTP parameters.

RFC 2132:

8.3. Network Time Protocol Servers Option

This option specifies a list of IP addresses indicating NTP [18]
servers available to the client. Servers SHOULD be listed in order
of preference.

The code for this option is 42. Its minimum length is 4, and the
length MUST be a multiple of 4.

Note the use of "SHOULD" as opposed to "MUST"

Malt
  • 28,965
  • 9
  • 65
  • 105