[ntp:questions] Source address in response not the same as target address in request

Rick Jones rick.jones2 at hp.com
Mon Oct 13 16:46:21 UTC 2008

Danny Mayer <mayer at ntp.isc.org> wrote:
> Rick Jones wrote:
> > If it simply sends via the socket on which the query was recieved,
> > having bound that socket to a given IP should result in that IP being
> > used as the source IP of the response.
> > 
> > Perhaps there is a reason to send via another socket, but as I'm
> > typing I cannot think of it.
> > 
> > rick jones

> NTP always replies on the same interface with the same IP address. It
> should never reply with a different IP address as the receiving end
> would drop it as invalid.

Did you mean to say "replies on the same socket?"  To a networking guy
"socket" is distinct from interface (eg NIC) and from the first hop
routing decision to be made by the stack.

Soooo, if NTP is replying on the same socket, and it _isn't_ the/a
wildcard socket, then the source IP's should already be correct and
the mystery would seem to deepen.

Might be a good idea for the OP to get a system call trace of NTP,
preferably including the creation and binding of the sockets and then
the receipt and sending of a response.

rick jones
oxymoron n, Hummer H2 with California Save Our Coasts and Oceans plates
these opinions are mine, all mine; HP might not want them anyway... :)
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

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