[mrtg] ifInOctets but no ifOutOctets.... ever seen this?

Gene Titus gene at ots.utsystem.edu
Tue Jul 20 17:40:37 CEST 2010

I've got a weird problem. I've run mrtg (and rtg) against Junipers routers,
cisco switches, and several other network device for many years. I generate
my own mrtg config files, create my own rrd files, and have custom graphing
routines. But I've never run into this problem.

We just add some cisco ios switches to our network. They're configured with
several "unrouted vlan". I can usually traffic monitor unrouted vlans
without problem. But on these switches, the unrouted vlans have ifInOctet
counters but no ifOutOctet counters.

Example: Look at ifindex 290 and 291. I included 288 and 289 for reference.
IF-MIB::ifIndex.288 = INTEGER: 288
IF-MIB::ifIndex.289 = INTEGER: 289
IF-MIB::ifIndex.290 = INTEGER: 290
IF-MIB::ifIndex.291 = INTEGER: 291

IF-MIB::ifDescr.288 = STRING: FastEthernet7/47
IF-MIB::ifDescr.289 = STRING: FastEthernet7/48
IF-MIB::ifDescr.290 = STRING: unrouted VLAN 981
IF-MIB::ifDescr.291 = STRING: unrouted VLAN 982

IF-MIB::ifInOctets.288 = Counter32: 0
IF-MIB::ifInOctets.289 = Counter32: 0
IF-MIB::ifInOctets.290 = Counter32: 2910395469
IF-MIB::ifInOctets.291 = Counter32: 130332220

IF-MIB::ifOutOctets.288 = Counter32: 0
IF-MIB::ifOutOctets.289 = Counter32: 0
That's it.... there are no more ifoutoctet entries.....

And of course mrtg poller is complaining that the ifOutOctets does not

Have anyone ever seen this?

The only fix I see is to change the Target line for these entries to query
the ifInOctets twice.

Gene Titus

Gene Titus
Sr Operating System Specialist
The Office of Telecommunication Services
The University of Texas at Austin
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