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Thijs Van Severen
Cisco Employee

configure GPS sync on ASR9006

Hi All,


i'm trying to set up timesync on my ASR9006 using GPS signals

i have connected the 1MHz + 1pps signals to the ASR, and i have followed these instructions (found here) to select these signals as clock source

RP/0/RSP0/CPU0:router# configure
RP/0/RSP0/CPU0:router(config)# clock-interface sync 2 location 0/rsp0/cpu0
RP/0/RSP0/CPU0:router(config-clock-if)# port-parameters
RP/0/RSP0/CPU0:router(config-clk-parms)# gps-input tod-format cisco pps-input rs422

i dont get any error message, but other than that i'm pretty much lost ...

there seems to be very little info available on the www about NTP sync using GPS signals

all tips are welcome !




Thijs Van Severen
Cisco Employee

Hi again,


I found some more info that seems to indicate that i need the GPS signals _and_ the ToD input

In an other document about PTP i found some info about GPS config (see this document), but i'm still puzzled how/if PTP and NTP can coexist ...


The ultimate goal is to sync the ASR to GPS, and then configure the ASR as (stratum 1) NTP server for my lab.


All tips are welcome




hi thijs,

this is the pinout:



Time of Day RS422



Time of Day RS422


config :

clock-interface sync 2 location 0/RSP0/CPU0
  gps-input tod-format cisco pps-input rs422
frequency synchronization
  selection input
  priority 1
  wait-to-restore 0
  ssm disable
  time-of-day-priority 1
  quality receive exact itu-t option 2 generation 2 PRS



Hi Xander

connections are done, config done (as described above)   :-)

is there a way to see if the ASR 'understands' what is coming in on the ToD connector (some debug ?) and if it can lock to the 1pps/10Mc inputs ?

the output of show freq synchronization selection location 0/rSP0/CPU0 remains the same ...


btw: i'm assuming that the spectracom is transmitting the ToD in DD/MM/YYYY format, and by default the ASR expects MM/DD/YYYY if i understand correctly

i'll hook up a pc to the rs232 out of the spectracom to see what exactly it is sending out




Hi again Xander

i just verified the ToD RS232 output of my GPS receiver :

ASCII, 9600 bps, 8 bits, 1 stop bit, odd parity

this is the output : 16/02/2015 08:34:37U     (dd/mm/yyyy hh:mm:ss)


so i'll have to figure out how to change this to on the Spectracom device

are there any requirements concerning baudrate ?


i have googled and googled but i'm baffled about the lack of documentation concerning GPS/ToD/NTP ...

thank god for forums like this and people like you Xander !





hi thijs,

yeah it is tricky business. the a9k uses 9600,8,N,1 as the design of this interface and operation was targeted to the symmetricom TS3500/TS3600

I am checking if there is any option to alter the uart to accept parity.

seems somewhat off to use parity these days, so I would also recommend checking with the gps vendor to see if they can alter their behavior.



hi Xander

i just got an answer from spectracom about the parity : it cant be changed :-(

did you find out anything about the ASR uart parity config ?




hi thijs,

darn... that spectracom :) (why using a parity and waste a bit on slow links for whatever purpose right, but hey...)

The DTI asic we are using for the timing interface and infrastructure has an embedded UART. I don't know if we can modify the UART settings or if it is flexible enough to make something happen.

We have a call in with our vendor for the DTI to see what the options are. If it is possible it will mean a new fpd image over the DTI, but when it comes to that, we'll take it from there. First we need to see how flexible this UART in the DTI is.

check back in next week if you dont hear from me before.


hi Xander


any update on this one ?





no breaking news yet, I am working with our asic vendor to see if they can help with the modification of the uart with a microcode change, but it seems like they dont really even know what a stopbit is :) sorry this is taking a while, unfortunately I am dependent on some others with this before we can make progress. I would want to recommend also to see if you can swap your device possibly for one that uses the right settings or has a configurable uart to attack it from 2 angles...



thanks fo rthe effort Xander, i appreciate it

btw: i recall that there was a discussion about a hybrid config somewhere but i cant seem to find it any more

IIRC it would allow you to get ToD form a NTP server, but still use the GPS 1pps and 10MHz inputs

does that ring a bell ?




yes I recall that part :)

today all 3 inputs are required for the internal PFM (platform fault manager) and the sync/timing not to call an alarm on a missing input.

this is a fix pending:

 CSCun86423    RSP GPS frequency port should function without TOD input

So you can still do it, but the timing logic will call it an "alarm" because the TOD is missing.



Xander, this is a great discussion.  My issue is that I keep losing NTP sources on my ASR for various reasons.  I see plenty NTP server boxes on the internet that use RS422, 10MHz and 1PPS.  If you had to pick one which would you pick and how would you connect it?

thank you :) for the development and verification we used the: Symmetricom TimeSource 3500 or 3600

the PPS/10mhz is rather standardized and not that much challenge. with the TOD I see some nuances in terms of how the TOD is provided or formatted actually.

so as long as your receiver follows the right standardization and formatting according to your config (gprmc or ntp4) you should be all set.

also it needs to be in rs422 signal output. some devices may have an rs232, which is fine too if we use an extra converter to make the async balanced.



Thanks for the feedback, I have two more questions :)

1.) Can I only hook up the TOD as the time source to an ASR 9001 assuming I use the latest code 5.3.3.MD?  Would this give me enough to replace using public NIST servers as my time source or do I have to hook up the PPS and 10MHz connection?  

2.) I found Cisco PN: CAB-T3E3-RF-BNC-M for BNC Male to 1.0/2.3 RF Male cable to connect to my unit but depending on where I look on Cisco it might be standard BNC or mini-BNC.  I need standard.  Any chance you can get clarification?  Really miss Radio Shack and stores like it now you have to mail order everything :)  shows it a standard BNC  shows it as mini BNC