Re: Pass-through control

On 09/05/07, Hartog, T. (Tim) <[email protected]> wrote:
> I'm trying to use the option pass-through control in netsnmp to create some
> kind of SNMP proxy.

Is there any reason to use the pass-through mechanism, rather than the "proxy"
directive which is intended for exactly this functionality?



> The snmp_test file contains the following code:
>
> #!/bin/bash

> if [ "$n_or_g" == "-g" ]; then
>         result_code=`$path/snmpget -O ne -v 1 -c $community $host_name $oid
> 2>/dev/null`
> else
>         result_code=`$path/snmpgetnext -O ne -v 1 -c $community $host_name
> $oid 2>/dev/null`
> fi

Ugh!  Why oh why do people *insist* on throwing away error messages?
You're a sysadmin - if something goes wrong, surely you want to know about it!
[Sorry - you pressed a button there]

> echo "The received snmp content: " $result_code

Shouldn't that output be directed to the log file?


> check_succeeded=$?
> echo $check_succeeded >>/tmp/snmp.log
> if [ "$check_succeeded" != "0" ] ; then
>         echo "And error occured." ;

and that?



> echo $new_oid $type $value >>/tmp/snmp.log

> echo "Nieuwe OID: "$new_oid
> echo "Type: "$type
> echo "Waarde: "$value

That is not the output format that the "pass" mechanism is expecting.
The extra tokens will confuse the master agent, and prevent this
script working as intended.
   Please re-read the snmpd.conf(5) description, and ensure that
the script output conforms to the format specified there.



> If i executed the snmp_test directly it works fine, but for some reason the
> pass-control function does not work at all. When i use an .1.3. oid on
> snmpget on localhost:11161 it should execute the script and get the data
> from the snmp-instance running on port 161. But for some reason i only get
> the results from the 11161 snmp instance.

Remember that the SNMP agent works on a "more-specific wins" model.
If you've got two registrations covering the same MIB object - one ("pass")
covering the whole of the subtree .1.3, and the other (internal) covering a
smaller portion of it - then the more specific (internal) registration will take
priority.
    I'd suggest that you run your tests with a more focussed target - preferably
one that's only implemented on the 161 agent.

Dave

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