[ntp:questions] server's address in ntp payload?

Danny Mayer mayer at gis.net
Fri Nov 18 14:24:34 UTC 2005

Ulisses wrote:
> Hello Danny
> On Thu, Nov 17, 2005 at 09:29:17PM -0500, Danny Mayer wrote:
>>Ulisses wrote:
>>>Hello all
> [...]
>>No you are not wrong, but why would you want to? 
> The usefulness I wanted with it is to try getting the
> loopback address of ntp servers running on routers

That's confusing me. Do you really mean the loopback addresss - and ::1 or did you mean an address bound to the interface?

> (for good purposes)
> Also It would be useful if I could extract from ntp, any 
> Globally Unique Identifier I could get from NTP protocol that
> could identify the same ntpd process in a multi-homed router.

There nearest thing to an identifier is the refid. Unfortunately it's
flawed in the NTP reference implmentation since you can get different
refid's from different addresses on the machine.

> The only reliable way to achieve it I have figured out is 
> (more or less) to extract the ntp stats and compare them when 
> possible
>>Are you asking about the server sending the packet? 
>  Host A                         Host B (Router)
>                      query
> ntpdc/ntpq/ntpd --------------> ntpd
>                 <-------------
>                      reply
> I want to know from Host A, the address of Host B looking an ntp header

I don't understand. Are you asking that, sitting at Host A, you send a
packet to host B and then you get in the response the address that Host
B sees as receiving the request from?

The answer is that it's the address of the interface receiving the
packet. There was a bug, long since fixed, which resulted in a packet
being returned to a different address.


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