[time-nuts] GPS, NTP, and Cisco routers...
mark.allwright at bell.ca
mark.allwright at bell.ca
Mon Oct 6 17:47:55 UTC 2008
I remember running this on "line aux 0" in the IOS version 11.x days (circa 1999). Was supported on the 7000, 4000 and 2500 series routers. It was originally designed for a Telecom Solutions (bought by Symmetricom) clock that would be co-located with the routers in a data centre . I have a PDF copy of "Application Note 600" that shows how it was intended to be used (mail me if you need a copy). I ditched the solution in favour of a FreeBSD+GPS based solution; Cisco was (and still is) only supporting version 3 of NTP specification. I do not have any data left on how well it worked but I recall it was better with the PPS support than without.
Mark Allwright CCIE #1088
National Hosting Services - Senior Data Analyst
2100 111 - 5th Avenue SW
Calgary, AB T2P 3Y6
T: 403 410-0733 | F: 403 216-6050
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Scott Mace
Sent: Sunday, October 05, 2008 11:33 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS, NTP, and Cisco routers...
This runs on the aux port, and the sup720 doesn't have an aux port...
There are always obscure features that slip into the production releases that aren't tested and they just forget to exclude them during builds.
TAC will probably have no clue about this...
You could try the cisco-nsp mailling list for support, but beware, it's frequented by cisco developers that will just as soon open a bug-id to drop 'feature' from the production release if it was never supposed to be there in the first place.
I wonder if this was originally used as an alternative method to time the MIX midplane in the VXR chassis and the NTP feature was side benefit? Most telecom gear that needs synchronization will take a BITS input or some other frequency reference. I've used that extensively with SONET gear and the good old Datum OT-21. I never used the 7200 MIX, so I'm not sure if it could take an external reference or just recover clock from a DS1 port.
Seems like a good use for an AUX port if you don't need a modem or reverse telnet!
Scott McGrath wrote:
> Actually you might get pretty good results if you have a 6509 as any
> activity on the serial port triggers a CPU interrupt which is why on a
> overloaded 6509 the first thing to try is "no logging console" to get
> the cpu down from 100% - usually in the context of DDoS and the
> control plane is slammed as the EOBC is only a 1 megabit channel even
> on the 3BXL's. This is one of the advantages of the annual trek out
> to Bldg 14 in San Jose - one gets to meet the guys who developed the
> code for the routers.
> This has more than passing interest for me as one could take a NovaTel
> GPSCard which has a 1PPS output and runs on a single 12-36V supply and
> has a dedicated 1PPS output at serial levels and install one at each
> router location. Still have not disassembled the 2501 and 2611 to
> see which cheapo TCXO Cisco has installed.
> What do you have available at your shop - we are running SUP720-3BXL's
> running 12.2 SXF
> On Sun, Oct 5, 2008 at 1:00 AM, Dave hartzell <hartzell at gmail.com> wrote:
>> Looks like Trimble and Cisco got together on a PPS implementation for
>> the 7200, starting with 12.0T trainwreck:
>> Since I don't have any 7200s any longer (thank goodness), I checked
>> and it seems that the 6500s support this as well on the console
>> 6509-rtr(config-line)#ntp ?
>> pps-discipline Use PPS pulse to discipline system clock
>> refclock NTP Reference Clock
>> 6509-rtr(config-line)#ntp refclock ?
>> telecom-solutions Telecom Solutions GPS
>> trimble Trimble Navigation TSIP Protocol
>> It looks interesting, and if the code is just looking for a PPS
>> transition on the CTS or RI, you might be in luck with any external
>> BUT be forewarned, IOS is a cooperative multitasking operating system
>> (at least prior to the new "modular" stuff), so your accuracy is
>> going to vary depending on loads, processes, etc. I wouldn't count
>> on this being to spectacular... probably no better than an external
>> NTP source.
>> And of course, you can always call the TAC for more assistance! ;-)
>> On Fri, Oct 3, 2008 at 2:39 PM, Robert Vassar <rvassar at rob-vassar.com> wrote:
>>> 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? :-)
>>> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to
>>> and follow the instructions there.
>> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to
>> and follow the instructions there.
> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to
> and follow the instructions there.
time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
More information about the time-nuts