NTP on DDR

I have a central PPP server (3640) and want my remote sites to sync thier
time when they connect once a day to download files.
But I don't want NTP to bring the line up itself.

How would I configure NTP on both sides to sync only when connected.

Thanks
Groper

 

In interesting traffic access-list deny NTP traffic.

Ivan

 

Interesting idea, just done some further research. What about if I were to
use

ppp Server 3640
!
Dialer0
ntp broadcast


remote 2620
!
BRI0/0
ntp broadcast client

Would this be better, or should I use a combination of both?

Thanks
Groper

 

OK, looks like the ntp broadcast keeps bringing the line up, not a desired
result.

On the interesting traffic access list, surly if I block ntp, I'll get no
sync at all

Thanks
Groper

 

You will, interesting traffic access-list is just for bringing line up (and
keeping it up), but it won't block anything when line is up. Just will
prevent ntp for bringing line up.

Ivan

 

You misunderstand. The interesting traffic 'access-list' is only what
causes dialing. It is unfortunated that it uses a think called
'access-list.' access-list really is just a data structure to describe a
group of IP addresses and service ports.

If you wanted to stop NTP traffic, you would need to add an "access-GROUP"
to the interface. "dialer-group" only controls dialing. So deny NTP only
on the dialer-group access list but not the access-group access list.

 

So make it uninteresting then.

You're not blocking the traffic when you make it uninteresting, you're
just telling the router to not bring/keep the link up on account of these
particular packets.

The traffic itself is still forwarded across the link.