RE: NTP recommedations

["Burton M. Strauss III" <BStrauss () acm org>]

Really, all you need to know is on the web pages, http://www.ntp.org.

My favs are the cookbook - http://www.umich.edu/~rsug/services/ntp.html (for
setting up your internal clients) and the FAQ,
http://www.ntp.org/ntpfaq/NTP-a-faq.htm - see section 6.2.1.3. How should I
provide NTP services for a huge network?

In the abstract - since I've never done it for real for more than a dozen
servers/hosts...

First off, are you going to run your own Stratum 1 server?
  It's not cheap to buy the gear, but you could then run it ENTIRELY inside
the firewall.

If you're really, really worried, then grab a hold of one of the Linux
distros that boots from a CD and customize it to be an ntp server and ONLY
an ntp server and stick THOSE in the dmz (Those are the 2a, 2b and 2c in the
diagram in the FAQ).  Configure them with a UPS that allows you to restart
the hardware on a schedule and remove the HD (all the dynamic files are in
RAM disk).  Yes, you lose the drift file, but since this is supposed to be
synced to a real time standard, who cares about the PC clock.  If somebody
roots the box, well, at 0-dark-and-scary, it reboots back to the original
configuration.

Then you put local (3a...) ntp servers in each site and configure servers &
workstations to use those as their standard.

If WAN connectivity is a problem, you could peer triplets of the 3s, either
locally redundant boxes or close by network (Detroit peers w/ Rochester and
Chicago) (Chicago peers with Detroit and Indianapolis) etc.


-----Burton



-----Original Message-----
From: Jennifer Fountain [mailto:JFountain () rbinc com]
Sent: Tuesday, March 11, 2003 7:32 PM
To: security-basics () securityfocus com
Subject: NTP recommedations


I am currently looking into configuring my company's time servers.  My
initial thoughts were setting up two or three in the dmz and configuring
them to update their time on a regular basis (haven't defined regular yet)
and then install two or three interal time servers that query these servers.
I currently have a web server, reverse proxy, ftp (blush embarrassed - going
to be getting rid of THIS real soon), email, ids, and two dns servers in the
dmz.  Someone has recommended to configure three of these servers (web, dns,
and email) as a time server.  At first, I say - huh - no.  That would mean
opening up two ports on each box and having a new set of potential problems
if i miss anying.  But I am not an expert so I head to google searches and
you for guidance.  Could anyone tell me their configuration or recommend a
"good" configuration for company time servers?

Thank you
Jenn

P.S  If anyone is at SANS 2003, ping me if you are in track 3 :)