[time-nuts] GPS, NTP, and Cisco routers...
Robert Vassar
rvassar at rob-vassar.com
Sun Oct 5 13:22:02 UTC 2008
It looks like the feature set varies significantly with the router
model, and by IOS feature set. The router I have here is an eBay
special, an old 2514. It's probably 10 years old, though I think
Cisco continued to make them until about 2003. It's only configured
with 8mb flash, so it can only run the stripped down IP subset.
(which lacks the IPv6 stuff I need too...) Every few years I dabble
with ploughing thru the CC** tests, but I'm a QA engineer, so it
never becomes a priority.
It's running c2500-i-l.121-27b.bin, and my ntp menu looks quite
different:
Router2#config t
Enter configuration commands, one per line. End with CNTL/Z.
Router2(config)#ntp ?
access-group Control NTP access
authenticate Authenticate time sources
authentication-key Authentication key for trusted time sources
broadcastdelay Estimated round-trip delay
clock-period Length of hardware clock tick
master Act as NTP master clock
max-associations Set maximum number of associations
peer Configure NTP peer
server Configure NTP server
source Configure interface for source address
trusted-key Key numbers for trusted time sources
Router2(config)#^Z
No "refclock" option. If I had a 16mb flash card, I could run the
"Enterprise" image, which might have different features. But a 16mb
flash card and FPM SIMM cost more than this router is worth. It
appears to be NTP v3 as well, though all my Solaris boxes run v3 due
to some issues with NTP 4.x and the kernel clock code. (It's being
fixed...)
I'll have to look at one of the newer models I have in the lab at
work. I've also been thinking of buying an 851w for my DSL line here
at the house. I've outgrown my WRT54G, even running Tomato, perhaps
I'll be pleasantly surprised. I hadn't even looked at Cisco stuff
since 2002 or so, certainly pre-12.1 anyway. I was just kind of
surprised to come across an NTP server at all, and I was curious what
its "Time-Nuts hackability" rating was. :-)
Thanks and 73,
Rob
KC6OOM/5
On Oct 5, 2008, at 12:00 AM, Dave hartzell 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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