ppp with dynamic IPs and ipfw "me"

Brad Knowles brad.knowles at skynet.be
Thu Jun 17 10:10:17 GMT 2004

At 11:36 AM +0200 2004-06-17, Oliver Fromme wrote:

>  I'm not sure if this is related to your problem, but you
>  have to kill and restart ntpd every time you get a new IP.
>  That's because ntpd binds to every IP address it finds upon
>  startup explicitely, not just to "*".

	BIND does the same thing.  If you're using UDP communications, 
you almost always need to make sure that you send the response packet 
on the same interface that you got the query from, and it's not 
possible to tell which interface a packet comes in on if you just 
listen to INADDR_ANY.

>  You can do that automatically with a ppp.linkup script.

	IIRC, there are a variety of shell scripts that have been posted 
to perform this function on the comp.protocols.time.ntp newsgroup.

	We should probably take those and work them into a more 
standard/robust form and include those in the contrib/ directory in 
the tarball.  That way, not only could they be used with FreeBSD, but 
they could also be used with other OSes which incorporate ntpd into 
their standard startup procedures (e.g., MacOS X).

	Disclaimer: I am a contributor to ntp.org, and I'm theoretically 
responsible for certain scripts found in the BIND contrib/ directory, 
but I don't think that this is an area that I'd be 
interested/willing/able to handle myself for NTP.  If you've got 
something to contribute in this area, I'd be glad to work with you 
and the other contributors to get that incorporated.

Brad Knowles, <brad.knowles at skynet.be>

"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."
     -Benjamin Franklin, Historical Review of Pennsylvania.

   SAGE member since 1995.  See <http://www.sage.org/> for more info.

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