[time-nuts] GPS, NTP, and Cisco routers...

Tom Arnold xyzzy at sysabend.org
Sat Oct 4 00:02:15 UTC 2008

On Fri, Oct 03, 2008 at 06:46:17PM -0400, time-nuts-request at febo.com wrote:
> From: Robert Vassar <rvassar at rob-vassar.com>
> Subject: [time-nuts] GPS, NTP, and Cisco routers...
> I've been fiddling around with an old Cisco router here at the house  
> to brush up.  We have an IPv6 project going at work, and our WAN  
> provider provides no native transit, so I'm looking at doing some  
> tunneling.  Anyhow... I discovered IOS 12.1 and above have native NTP  
> capability.  I don't have the exhaustive IOS command reference, and I  
> suspect it's a limited NTP implementation. I'm wondering if it's  
> possible to tie a GPS unit to a router serial port and gain a stratum  
> 0 refclock.
> Any Cisco guru's on the list?  :-)

Cisco routers have a fairly basic NTP capability.  No chance right now of
using the serial port to speak to a GPS or synced clock on 90% of the gear.
I can't say for certain on some of the really high-end stuff but I kinda
doubt it.

Its really only intended for redistribution, heck, you can even *set* what
Stratum you claim to be ( by default I think Cisco uses 8 ).   The only
"extra" features they support is they will do ntp/multicast which is nice
from a client config point of view for us at least.

I'm using a pair of Endrun CDMA based ntp servers because they will work
inside a colo without external antennas, they sync our Cisco cores which
multicast out to the clients.  We're within a few milliseconds which is
close enough.  For redistribution to customers we sync a bunch of unix ntp
servers directly off the CDMA servers so our customers get Stratum 2.  I
hope to be adding a third Endrun box to the mix shortly where I can put up
an external GPS antenna...

 - Tom Arnold           -  "...is it a virus, a drug, or a religion?"  
 - Sysabend Caretaker   -    Juanita Shrugs. "What's the difference?"
 ------------------------       -- Neal Stephenson,  Snow Crash 

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