[c-nsp] Buggy Cisco SNMP traffic monitoring with MRTG

[Scott Weeks]

:: I've configured SNMP monitoring with MRTG for several Cisco switches.
:: When I configure MRTG to lo Fa0/13 it logs as Fa0/21 and visa versa.

:: I was thinking to automate the MRTG config-generation process for
:: integration in our pannel. Why does Cisco (a Cisco 3550 running layer3)
:: change the naming of ethernet ports?

:: It would be more logical to keep the snmp-target and numbering of Fa
:: ports the same as other brands do.

: > The 13 is the SNMP Interface Identifier, not the number of the interface.
: > Make sure to read all the MRTG documentation.  All the info is in there.
: > Snipping out the extra info in the email, you can see that the Interface
: > Identifier for Fa 0/13 is 21  So, when you're looking at Interface
: > Identifier 13 you're seeing the traffic on interface Fa 0/17.
:
: Sure, I already said that in my first post. But I want to know *why* it
: switches. I have 39 Cisco 39 available and it's only 1 switch who
: switches snmp identifiers.


Not all other brands number the SNMP Interface Identifiers the same as the
ethernet port numbers.  Some brands do that within a product line and not
other lines (at least Foundry).  Your output, though, looks like a bug
discussed here a while back.  Is this the same software as all the other
switches?  Also, there used to be an option in MRTG that allowed you to
not worry about the changing Interface Identifiers.

Good Luck,
scott






original message:
---------------------

Hello all,

I've configured SNMP monitoring with MRTG for several Cisco switches. When
I configure MRTG to lo Fa0/13 it logs as Fa0/21 and visa versa.

If you run cfgmaker (for MRTG) it generates the folowing config.

### Interface 13 >> Descr: 'FastEthernet0/17' | Name: 'Fa0/17' | Ip: '' |
Eth: '' ###

Target[XXX_13]: 13:XXXX at YYYY:
SetEnv[XXX_13]: MRTG_INT_IP="" MRTG_INT_DESCR="FastEthernet0/17"
MaxBytes[XXX_13]: 1250000
Title[XXX_13]: Traffic Analysis for 13 -- XXXX
PageTop[XXX_13]: <H1>Traffic Analysis for 13 -- XXXX</H1>
  <TABLE>
    <TR><TD>System:</TD>     <TD>XXXX in </TD></TR>
    <TR><TD>Maintainer:</TD> <TD></TD></TR>
    <TR><TD>Description:</TD><TD>FastEthernet0/17  </TD></TR>
    <TR><TD>ifType:</TD>     <TD>ethernetCsmacd (6)</TD></TR>
    <TR><TD>ifName:</TD>     <TD>Fa0/17</TD></TR>
    <TR><TD>Max Speed:</TD>  <TD>10.0 Mbits/s</TD></TR>
  </TABLE>

Notice the 13 (Fa0/13) to be monitored? If you put traffic through Fa0/17
it will show up on the
statistics for port 13?

Is this behaviour normal? The folowing is some strange output on MRTG.

--snpo: confcache XXX at YYY: Name Fa0/1 --> 1
--snpo: confcache XXX at YYY: Name Fa0/2 --> 2
--snpo: confcache XXX at YYY: Name Fa0/3 --> 3
--snpo: confcache XXX at YYY: Name Fa0/4 --> 4
--snpo: confcache XXX at YYY: Name Fa0/5 --> 5
--snpo: confcache XXX at YYY: Name Fa0/6 --> 6
--snpo: confcache XXX at YYY: Name Fa0/7 --> 7
--snpo: confcache XXX at YYY: Name Fa0/8 --> 8
--snpo: confcache XXX at YYY: Name Fa0/9 --> 9
--snpo: confcache XXX at YYY: Name Fa0/10 --> 10
--snpo: confcache XXX at YYY: Name Fa0/11 --> 11
--snpo: confcache XXX at YYY: Name Fa0/12 --> 12
--snpo: confcache XXX at YYY: Name Fa0/17 --> 13
--snpo: confcache XXX at YYY: Name Fa0/18 --> 14
--snpo: confcache XXX at YYY: Name Fa0/19 --> 15
--snpo: confcache XXX at YYY: Name Fa0/20 --> 16
--snpo: confcache XXX at YYY: Name Fa0/21 --> 17
--snpo: confcache XXX at YYY: Name Fa0/22 --> 18
--snpo: confcache XXX at YYY: Name Fa0/23 --> 19
--snpo: confcache XXX at YYY: Name Fa0/24 --> 20
--snpo: confcache XXX at YYY: Name Fa0/13 --> 21
--snpo: confcache XXX at YYY: Name Fa0/14 --> 22
--snpo: confcache XXX at YYY: Name Fa0/15 --> 23
--snpo: confcache XXX at YYY: Name Fa0/16 --> 24
--snpo: confcache XXX at YYY: Name Gi0/1 --> 25
--snpo: confcache XXX at YYY: Name Gi0/2 --> 26
--snpo: confcache XXX at YYY: Name Nu0 --> 27
--snpo: confcache XXX at YYY: Name Vl1 --> 28
--snpo: confcache XXX at YYY: Name Lo1 --> 29
etc...

I was thinking to automate the MRTG config-generation process for
integration in our pannel. Why
does Cisco (a Cisco 3550 running layer3) change the naming of ethernet
ports?

It would be more logical to keep the snmp-target and numbering of Fa ports
the same as other brands do.

Regards,
Geert Hauwaerts.