[time-nuts] GPS, NTP, and Cisco routers...
scmcgrath at gmail.com
Sun Oct 5 16:43:31 UTC 2008
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 serial
> 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
> 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? :-)
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