Working a whole device with Net::SNMP with Perl

Hi,

I'm trying to figure out how to walk a whole device using Net::SNMP in
perl. I have done a few other just basic gets with it and I can't figure
out how to do a walk with it.

Thank you for the help.

Thomas

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2008/6/10 Thomas Bonham <thomasbonham@bonhamlinux.org>:
> I'm trying to figure out how to walk a whole device using
> Net::SNMP in perl.

$ man SNMP

$vb = new SNMP::Varbind();
do {
$val = $sess->getnext($vb);
print "@{$vb}\n";
} until ($sess->{ErrorNum});



Dave

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> From: Thomas Bonham [mailto:thomasbonham@bonhamlinux.org]

> I'm trying to figure out how to walk a whole device using Net::SNMP in
> perl

Can't help you with Perl scripts, but if you just want to verify
instrumented MIBs:

<command line>

snmpwalk -c public -v 2c <10.10.10.10> iso

This will walk the SNMP agent at IP address 10.10.10.10 using v2c
protocol and community string "public," starting at the top MIB node.

Ron



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>>>>> On Tue, 10 Jun 2008 05:08:11 -0700, Thomas Bonham <thomasbonham@bonhamlinux.org> said:

TB> I'm trying to figure out how to walk a whole device using Net::SNMP in
TB> perl.

We aren't affiliated with the Net::SNMP perl module; the module that
binds to the Net-SNMP package is "SNMP" instead (in which case, Dave's
answer is spot on)
--
Wes Hardaker
Sparta, Inc.

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Wes Hardaker wrote:
>>>>>> On Tue, 10 Jun 2008 05:08:11 -0700, Thomas Bonham <thomasbonham@bonhamlinux.org> said:
>>>>>>
>
> TB> I'm trying to figure out how to walk a whole device using Net::SNMP in
> TB> perl.
>
> We aren't affiliated with the Net::SNMP perl module; the module that
> binds to the Net-SNMP package is "SNMP" instead (in which case, Dave's
> answer is spot on)
>
I didn't know that.

Maybe someone can tell me why I'm getting a error here with this little
bit of perl.

Code:
#/usr/bin/perl -w
$host = "localhost";
$st="public";
$sess = new SNMP::Session(DestHost=>$host,Community=>$st);
$val = $sess->get("sysDescr.0");
die $sess->{ErrroStr} if($sess->{ErrorStr});

Error: Unknow user name at test.pl line 7.

Thank you,

Thomas

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> From: net-snmp-users-bounces@lists.sourceforge.net
> [mailto:net-snmp-users-bounces@lists.sourceforge.net] On
> Behalf Of Thomas Bonham
> Sent: Tuesday, June 10, 2008 10:17 AM

> Wes Hardaker wrote:
> >>>>>> On Tue, 10 Jun 2008 05:08:11 -0700, Thomas Bonham
> <thomasbonham@bonhamlinux.org> said:
> >>>>>>
> >
> > TB> I'm trying to figure out how to walk a whole device
> using Net::SNMP in
> > TB> perl.
> >
> > We aren't affiliated with the Net::SNMP perl module; the module that
> > binds to the Net-SNMP package is "SNMP" instead (in which
> case, Dave's
> > answer is spot on)
> >
> I didn't know that.

Details, originally from Dave:

http://www.net-snmp.org/wiki/index.p...e_should_I_use

> Maybe someone can tell me why I'm getting a error here with
> this little
> bit of perl.
>
> Code:
> #/usr/bin/perl -w
> $host = "localhost";
> $st="public";
> $sess = new SNMP::Session(DestHost=>$host,Community=>$st);
> $val = $sess->get("sysDescr.0");
> die $sess->{ErrroStr} if($sess->{ErrorStr});
>
> Error: Unknow user name at test.pl line 7.

"User name" is an SNMP v3 concept, but you are setting a community, which implies v1/v2c operation. You need to find and set the thingy that determines the SNMP version. Sorry I can't give more detail, but I gleefully discarded perl years ago...


HTH,

Mike

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Wes Hardaker wrote:
>>>>>> On Tue, 10 Jun 2008 10:16:20 -0700, Thomas Bonham <thomasbonham@bonhamlinux.org> said:
>>>>>>
>
> TB> Error: Unknow user name at test.pl line 7.
>
> That indicates it's defaulting to SNMPv3 (which is the standard default)
> and the remote agent doesn't have a user matching what you sent.
>
> Use Version => 2c or Version => 1 instead if you want SNMPv2c or SNMPv1.
>
Okay now everything is working.

The only other big thing that I need to figure out how to do is tell it
to just work one little part of something. As a example just have it
work "system" I can't seem to figure that out. Right now I'm working on
one function that will walk "ipAdEntAddr" to get all of the ip address
on the system then from there I will pull then index's of them to I can
then go look it up with the device index.

Thanks for all of the help.

Thomas

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2008/6/11 Thomas Bonham <thomasbonham@bonhamlinux.org>:
> The only other big thing that I need to figure out how to do is tell it
> to just work one little part of something. As a example just have it
> work "system"

There are two aspects to this:
- how to tell it where to start
- how to tell it where to stop


You can specify a starting point when you create the initial
Varbind object. Instead of simply

$vb = new SNMP::Varbind();
try
$vb = new SNMP::Varbind(["system"]);

Telling it where to stop is handled by the termination condition
at the end of the look. The initial code fragment I posted used

do {
...
} until ($sess->{ErrorNum});

which keeps going until it reaches the end.
Try something like:

do {
...
} until (${$vb}[0] !~ /^sys/ );

which will print the system group only.

That's not exactly right, since it will actually print
the first entry *after* the system group as well,
before realising that it should have finished.
This might be better re-worked to use a while loop
instead.
And you might find a different test works
better for you. But that shows the basic idea.

Dave

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[ First - *please* don't mail me privately, without copying
any responses to the mailing list. I don't have the time
or inclination to offer private, unpaid, SNMP consultancy.
Keep discussions to the list, where others can both learn
and offer advice. Thanks. ]


2008/6/11 Thomas Bonham <thomasbonham@bonhamlinux.org>:
>>> The only other big thing that I need to figure out how to do is tell it
>>> to just work one little part of something. As a example just have it
>>> work "system"
>>>
>>
>> There are two aspects to this:
>> - how to tell it where to start
>> - how to tell it where to stop
>>
>>
>> You can specify a starting point when you create the initial
>> Varbind object. Instead of simply
>>
>> $vb = new SNMP::Varbind();
>> try
>> $vb = new SNMP::Varbind(["system"]);
>>
>> Telling it where to stop is handled by the termination condition
>> at the end of the look. The initial code fragment I posted used
>>
>>
>
> This part I don't get. I does it matter if I put the "system" mib in the
> "[]" because of the fact it will still go on after the system mib is out.

Yes - because the ["system"] bit is concerned with where the
walk *starts*, not where it stops.

Try running this script with ["system"] and look at the first two or
three lines of output. Then change the script to use ["ifTable"]
and run it again. You should see that the output begins at
(or shortly after) the specified point.

But this is *only* concerned with the starting point.
It has no effect on when the walk ends.
That's covered by the next bit of my earlier response:

>> do {
>> ...
>> } until ($sess->{ErrorNum});
>>
>> which keeps going until it reaches the end.
>> Try something like:
>>
>> do {
>> ...
>> } until (${$vb}[0] !~ /^sys/ );
>>
>> which will print the system group only.

Note the change to the exit condition here.



> So say to walk "ipAdEntAddr" to get the ip address on my computers. What I
> would have to do is to look for where it start and where it ends?


You would specify where it starts using

$vb = new SNMP::Varbind(["ipAdEntAddr"]);

You would specify where it ends by putting a suitable test
in the "until" check above.



> I do just the basic idea and I will problem try and rework it into a while
> loop because I think it will be simply easer to look for the start and the
> stop of some of the "mib" that I'm going to be using.
>
> Also I do plain on sharing this function when I get it done.
>
> Thanks for all of the help and know that this isn't like most question that
> I see through this group.

Dave

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