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

Scott Mace smace at intt.net
Sun Oct 5 17:32:51 UTC 2008


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

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:
>>
>> http://www.cisco.com/en/US/docs/ios/12_1t/12_1t1/feature/guide/dtrimble.html
>>
>> 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 serial
>> port:
>>
>> 6509-rtr(config-line)#ntp ?
>>  pps-discipline  Use PPS pulse to discipline system clock
>>  refclock        NTP Reference Clock
>>
>> and
>>
>> 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
>> PPS...
>>
>> 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!  ;-)
>>
>> 73,
>> Dave
>> AF6KD
>>
>>
>> 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?  :-)
>>>
>>>
>>>
>>> Cheers,
>>>
>>> Rob
>>>
>>>
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