[mrtg] DSCP/COS stats on Cisco router

Wed Sep 24 16:48:15 CEST 2014

The existence of multiple class-default graphs has to do with the cbQosParentObjectsIndex table. This table allows the script to derive the class map name to index number relationship for obtaining the actual qos stat OIDs but it also has functionality concerning match statement and policy map relationships. Because of this the name "class-default" effectively gets overloaded. The choice from the MRTG target generation perspective was either ignore everything named "class-default" or create multiple targets as "class default.<indexnum>". I chose the latter path because my network engineers tell me that the class-default stats are very useful to them even with the ambiguity of multiple class name, index number pairs. 
The obvious down side is which class-default means what and that is something I leave up to the qos experts who actually configure the routers in my network. My area of focus is stats collection, export, graphing, and alarming, not qos. Sorry I can't provide a more useful answer.

Since you probably have more qos background than I do, it may be useful for you to execute some snmpwalk commands and observe the output. 

Notice in this command that class-default belongs to index number 1593

mrtg at myserver> snmpwalk -v2c -c public myrouter .1.3.6.1.4.1.9.9.166
SNMPv2-SMI::enterprises.9.9.166.1.7.1.1.1.1593 = STRING: "class-default"
SNMPv2-SMI::enterprises.9.9.166.1.7.1.1.2.1593 = ""
SNMPv2-SMI::enterprises.9.9.166.1.7.1.1.3.1593 = INTEGER: 3
mrtg at myserver>

However, in the next command, index number 1508241 gets associated with index number 1593 which we established above as class-default.

mrtg at myserver> snmpwalk -v2c -c public myrouter .1.3.6.1.4.1.9.9.166
SNMPv2-SMI::enterprises.9.9.166.1.5.1.1.2.66.15082481 = Gauge32: 1593 <- class-default association to 1593 and 15082481  
SNMPv2-SMI::enterprises.9.9.166.1.5.1.1.3.66.15082481 = INTEGER: 2
SNMPv2-SMI::enterprises.9.9.166.1.5.1.1.4.66.1907667 = Gauge32: 15082481 <- additional unique index to index associations
SNMPv2-SMI::enterprises.9.9.166.1.5.1.1.4.66.9319458 = Gauge32: 15082481 <- additional unique index to index associations
SNMPv2-SMI::enterprises.9.9.166.1.5.1.1.4.66.9918016 = Gauge32: 15082481 <- additional unique index to index associations
<actual qos counter stats for 15082481 begin here>
SNMPv2-SMI::enterprises.9.9.166.1.5.1.1.4.66.15082481 = Gauge32: 66
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.1.66.15082481 = Counter32: 13
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.2.66.15082481 = Counter32: 3097686382
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.3.66.15082481 = Counter64: 58932261230
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.4.66.15082481 = Counter32: 12885
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.5.66.15082481 = Counter32: 783527026
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.6.66.15082481 = Counter64: 55341437135986
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.7.66.15082481 = Gauge32: 23843000
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.8.66.15082481 = Counter32: 12884
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.9.66.15082481 = Counter32: 865096188
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.10.66.15082481 = Counter64: 55337223737852
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.11.66.15082481 = Gauge32: 23823000
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.12.66.15082481 = Counter32: 0
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.13.66.15082481 = Counter32: 2883500
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.14.66.15082481 = Counter64: 2883500
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.15.66.15082481 = Counter32: 0
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.16.66.15082481 = Counter32: 4213398134
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.17.66.15082481 = Counter64: 4213398134
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.18.66.15082481 = Gauge32: 20000
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.19.66.15082481 = Counter32: 0
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.20.66.15082481 = Counter32: 0
SNMPv2-SMI::enterprises.9.9.166.1.15.1.1.21.66.15082481 = Counter64: 0
mrtg at myserver>

>There are no drops showing up, but the two Pre/Post graphs 
>appears to be the same.
>Can you help me understand what these represent?

Just fyi, my multiple class-default graphs on the same router are indeed significantly different.

It is also interesting to note that the only class map name that I have seen that leads to multiple name-index pairs is "class-default". This leads me to believe that there is something special about the "class-default" name since it never happens with other class-map/policy-map names.

-----Original Message-----
From: Alan Lehman [mailto:alehman at gbateam.com] 
Sent: Wednesday, September 24, 2014 8:50 AM
To: Volk,Gregory B; mrtg at lists.oetiker.ch
Subject: RE: DSCP/COS stats on Cisco router

Greg,
Thank you again for sharing your script. It seems to work well with my 2901. I do have a question regarding something I'm seeing in the output. I get four graphs for class-default:

class-default.4419217 drops
class-default.4419217 Pre/Post Policy bit rate
class-default.14664689 drops
class-default.14664689 Pre/Post Policy bit rate

There are no drops showing up, but the two Pre/Post graphs appears to be the same.
Can you help me understand what these represent?

-----Original Message-----
From: Volk,Gregory B [mailto:greg.volk at edwardjones.com] 
Sent: Monday, September 22, 2014 7:44 AM
To: Alan Lehman; mrtg at lists.oetiker.ch
Subject: RE: DSCP/COS stats on Cisco router

I've attached cbqos-cfgmaker.txt. This is a perl script that I wrote using mib variables defined in CISCO-CLASS-BASED-QOS-MIB and CISCO-CLASS-BASED-QOS-CAPABILITY. I've had reasonably good luck with it running against several Cisco models including 2900, 6509, 7304, ASR1003, and even all the way back to 7206XVR.

One downside to it is that the cbQosIfIndex instance numbers are not necessarily static through some config changes and reboots, but those are rare enough in my environment that it hasn't been a major issue for me.

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-----Original Message-----
From: mrtg [mailto:mrtg-bounces+greg.volk=edwardjones.com at lists.oetiker.ch] On Behalf Of Alan Lehman
Sent: Friday, September 19, 2014 3:44 PM
To: mrtg at lists.oetiker.ch
Subject: [mrtg] DSCP/COS stats on Cisco router

Hello,
I’m new to this list, but have been using mrtg for ages. Recently we implemented COS on our MPLS network. I would like to be able to see traffic on our Cisco 2901 broken down by COS/DSCP classification. Has anyone been able to accomplish this?
Thanks,
Alan

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