[collectd] SNMP Sub-OID Question

David Mitchell mitchell at ucar.edu
Tue Nov 24 16:05:31 CET 2009

David Mitchell wrote:
> Greetings,
> I'm trying to get the SNMP plugin to monitor client statistics on my
> wireless access points and have run into a little problem. The Cisco
> AP's I have use a fairly long instance in this table which includes the
> MAC address. Collectd only seems to use the last single OID from the
> instance in the name of the value. In my case, this ends up being the
> last octet of the clients MAC address. Unfortunately, there is no table
> I can use to map the instances via the "Instance" configuration option.
> I quick perusal of the code seems to show that the single-value suboid
> seems fairly hard-coded in. Is there any workaround for this? Have
> others hit this issue? A search in the bug tracker didn't turn anything up.

I've been looking into this more. I found a similar issue when using the
Instance option. Our AP's do include an IP address for each client which
I can use to map the Instance. But it's returned in a raw format of four
octets. Collectd prints this to the value name as though it was a
string, resulting in unprintable characters in the filename.

I think both of these issues can be rectified by calling back into
net-snmp to let it do the formatting needed for the values. I've begun
trying to patch up a version which does this. Is this a patch which is
likely to be accepted? I imagine that in some instances it will cause
changes in the resulting value name. Is such a patch likely to be
accepted? Do I need to perhaps include some non-default configuration
option to active it?

-David Mitchell

| David Mitchell (mitchell at ucar.edu)       Network Engineer IV  |
| Tel: (303) 497-1845                      National Center for  |
| FAX: (303) 497-1818                      Atmospheric Research |

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