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

[Belgian Network Solutions - Geert Hauwaerts]

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.
-- 
Network Operations Manager  - Belgian Network Solutions
Mobile: +32 (0)498 75 80 68 - Office: +32 (0)16 89 32 41
E-Mail: geert at benesol.be    - Online: http://www.benesol.be