[mrtg] Re: Mrtg for the latency of a link connected end to end on routers

[Daniel J McDonald]

> Subject: [mrtg] Mrtg for the latency of a link connected end to end on
> routers
>
> Hi all,
>         Can anyone help me on this

I thought you were given a pretty clear answer by an earlier poster that
there is nothing built into the router to give you this number unless you
are willing to figure out the RTR mib.

That being said, I did think of another latency sensitive application that
keeps track of such things: NTP.

You could graph cntpPeersDelay, assuming you were sending NTP over that
link, and assuming you were using RRDTOOL for the decimal support.

[dmcdonald at netmon dmcdonald]$ snmpwalk -m CISCO-NTP-MIB 172.16.29.1 public
cntpPeersDelay -IR -Os
cntpPeersDelay.57751 = 0.4119 seconds
[dmcdonald at netmon dmcdonald]$ snmpwalk -m CISCO-NTP-MIB 172.16.29.1 public
cntpPeersDelay -IR -On
1.3.6.1.4.1.9.9.168.1.2.1.1.24.57751 = 0.4119 seconds

it read .4149 seconds a little bit ago, so it looks like it is sensitive to
traffic....
and here is another circuit that is a full T1 instead of a 438 K dsl line:
[dmcdonald at netmon dmcdonald]$ snmpwalk -m CISCO-NTP-MIB 172.16.18.1 public
cntpPeersDelay -IR -On
1.3.6.1.4.1.9.9.168.1.2.1.1.24.24029 = 0.1797 seconds
So it is sensitive to serialization delay as well...
Ok, here is the first one a bit later:
[dmcdonald at netmon dmcdonald]$ snmpwalk -m CISCO-NTP-MIB 172.16.29.1 public
cntpPeersDelay -IR -On
1.3.6.1.4.1.9.9.168.1.2.1.1.24.57751 = 0.4178 seconds

so it definitely is continually checking the latency.

Note that this requires fairly recent versions of IOS.  I believe it is
supported in 12.1.5T, but not 12.1.3T.  I also see it on 12.1.5YB

Since NTP has to calculate the latency for its own purposes, this would at
least give you an apples-to-apples number.  Not that it would mean very much
beyond that, since it include processor latency and some CPU calculation
latency.  But it's something without the complexity of RTR.




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