Re: [Devmon] New template for collision detection on Cisco 3550

[W.J.M. N. <ne...@nl...>]

> On Friday 04 April 2008 16:03:33 W.J.M. Nelis wrote:
>> Hello,
>>
>> we've been using Hobbit / Devmon for a few months now. One problem we found
>> is that often high collision (red) rates were reported on back-up trunks.
>> It was found that this is caused by using the variable ifOutPktsSec, the
>> average number of packets per second. However, if the number of packets per
>> 5-minute interval is less than 300, this variable will have the value zero.
>> This causes the value of the collision rate to become 1.0. On a back-up
>> trunk, the packet-rate often is less than 1.0 packet per second.
>>
>> We've modified the templates of cisco_3550/if_col in the following way:
>>
>> [hobbit if_col]$ cat oids.old
>> ifName          : .1.3.6.1.2.1.31.1.1.1.1       : branch
>> ifAlias         : .1.3.6.1.2.1.31.1.1.1.18      : branch
>> ifBps           : .1.3.6.1.2.1.2.2.1.5          : branch
>> ifOutCollisions : .1.3.6.1.4.1.9.2.2.1.1.25     : branch
>> ifOutPktsSec    : .1.3.6.1.4.1.9.2.2.1.1.9      : branch
>> [hobbit if_col]$ cat oids
>> ifName                  : .1.3.6.1.2.1.31.1.1.1.1       : branch
>> ifHCOutUcastPkts        : .1.3.6.1.2.1.31.1.1.1.11      : branch
>> ifHCOutMcastPkts        : .1.3.6.1.2.1.31.1.1.1.12      : branch
>> ifHCOutBcastPkts        : .1.3.6.1.2.1.31.1.1.1.13      : branch
>> ifAlias                 : .1.3.6.1.2.1.31.1.1.1.18      : branch
>> ifOutCollisions         : .1.3.6.1.4.1.9.2.2.1.1.25     : branch
>>
>> [hobbit if_col]$ cat transforms.old
>> # Convert our total ifc octets(bytes) into bits
>> ifOutCps        : DELTA         : {ifOutCollisions}
>>
>> # Create our REAL packets per second
>> ifOutPps        : MATH          : {ifOutCps} + {ifOutPktsSec}
>>
>> # Determine percentage of packets that are collisions
>> ifOutColPct     : MATH          : ({ifOutCps} / {ifOutPps}) x 100
>>
>> # Create an alias in a bracketed box, or nothing if alias is blank
>> ifAliasBox      : REGSUB        : {ifAlias} /(\S+.*)/ [$1]/
>>
>> [hobbit if_col]$ cat transforms
>> # Fetch output packet rates and the collision rate
>> ifOutUP         : DELTA         : {ifHCOutUcastPkts}
>> ifOutMP         : DELTA         : {ifHCOutMcastPkts}
>> ifOutBP         : DELTA         : {ifHCOutBcastPkts}
>> ifOutC          : DELTA         : {ifOutCollisions}
>>
>> # Compute the total output packet rate, such that the collision ratio
>> # is at most 1.00
>> ifOutPkts       : MATH          : {ifOutUP} + {ifOutMP} + {ifOutBP} +
>> {ifOutC}
>>
>> # Determine number of collisions per 100 packets
>> ifOutColPct     : MATH          : ({ifOutC} / {ifOutPkts}) x 100
>>
>> # Create an alias in a bracketed box, or nothing if alias is blank
>> ifAliasBox      : REGSUB        : {ifAlias} /(\S+.*)/ [$1]/
>>
>>
>> Since this modification, we haven't had a single false red on
>> collision-rate.
> 
> From an initial look, it looks correct, but I won't have time to
> 
> Just to assist in seeing the differences, and applying them, can you post
> diffs instead, e.g. the output of:
> 
> diff -u transforms.old transforms

Here are the diffs:

[hobbit if_col]$ diff -u transforms.old transforms
--- transforms.old      2007-12-03 13:45:59.000000000 +0100
+++ transforms  2008-01-04 14:01:33.000000000 +0100
@@ -1,11 +1,15 @@
-# Convert our total ifc octets(bytes) into bits
-ifOutCps       : DELTA         : {ifOutCollisions}
+# Fetch output packet rates and the collision rate
+ifOutUP                : DELTA         : {ifHCOutUcastPkts}
+ifOutMP                : DELTA         : {ifHCOutMcastPkts}
+ifOutBP                : DELTA         : {ifHCOutBcastPkts}
+ifOutC         : DELTA         : {ifOutCollisions}

-# Create our REAL packets per second
-ifOutPps       : MATH          : {ifOutCps} + {ifOutPktsSec}
+# Compute the total output packet rate, such that the collision ratio
+# is at most 1.00
+ifOutPkts      : MATH          : {ifOutUP} + {ifOutMP} + {ifOutBP} + {ifOutC}

-# Determine percentage of packets that are collisions
-ifOutColPct    : MATH          : ({ifOutCps} / {ifOutPps}) x 100
+# Determine number of collisions per 100 packets
+ifOutColPct    : MATH          : ({ifOutC} / {ifOutPkts}) x 100

  # Create an alias in a bracketed box, or nothing if alias is blank
  ifAliasBox      : REGSUB        : {ifAlias} /(\S+.*)/ [$1]/


Regards,
   Wim Nelis.