<=
b>
Discovering SNMP Device Components
Pr=
e-requisite
and Target Audience
The article is mainly targeted to Partners and MP authors who
want to create MPs that discover SNMP devices components. Familiarity and
knowledge of writing basic SNMP monitoring MP is assumed.=
To learn more about writing MP to discover SNMP devices, che=
ck
out a great article published by Raphael Burri in his blog about SNMP Discovery Pro=
vider
for OpsMgr 2007. Other resources available include <=
/span>David Allen's Guide to SNMP Probe B=
ased
Monitors and Scott Vintiner’s Detailed walkthrou=
gh on
using the SNMP Discovery Provider.
Op=
sMgr
2007 and SNMP Discovery
With SNMP support, most customers would assume the ability to
discover and monitor their network devices is straightforward. Unfortunatel=
y,
this is not the case, as one quickly hits roadblocks in trying to discover =
and
monitor interfaces (or other components) on an SNMP device. The story becom=
es
even more difficult to explain, with SCE (supposedly less functional) able =
to
provide an Out-of-Box experience for network monitoring with the ability to
discover Network Device interfaces etc., which are SNMP components.
The OpsMgr 2007 SP1, the solution is to use the SnmpProbe mo=
dule
with the Walk config set to TRUE to walk SNMP table, and write a managed co=
de
mapper to process the returned discovery DataItem which is one big blob. Th=
is
is great if you are willing to write managed code. In fact, this is the
approach used in the SCE Network Monitoring MP. Alternatively, you can writ=
e a
script to map the discovery data. Idan has published a great article in his
blog on how to use script for discovery data mapping in Monitoring Network
Switches and Interfaces.
Another approach is to create a discovery rule for each
component. This necessitates knowing the number of components (e.g. interfa=
ces)
in advance which is unacceptably inflexible. For a switch with 48 ports, you wil=
l need
to create 48 discovery rules, one for each port. Surely, this cannot be fun.
Even then, this could get tricky since table entries are not guaranteed to =
be
sequential. For example, a table of management ports could have ifindex val=
ues
of 1, 2, 3, 4, 1002, 2001 etc. In this case, even knowing the number of
interfaces might not be enough.
OpsMgr 2007 R2 and SNMP Discovery
Enhancements in R2 provide the ability to discover and monit=
or components
of SNMP devices (usually expressed in SNMP tables) without the need to write
managed code discovery mapper. The enhancement also avoids the need to know
the number of components upfront and, thus, the need to create a disco=
very
rule for each component.
To take advantage of the enhancements in R2 to discover
components of an SNMP device, the following MP elements needs to be created=
by
editing the xml file of an MP:
1. =
Create a composite DataSource module to us=
e the
SnmpProbe module that walks the Index column of the SNMP Table. It will cre=
ate
an instance for each entry with only the index property populated. This mod=
ule
will take OID of the table index as a config:
![](3D"SNMPBasedMonitoring-DiscoveryDevicecomponents_files/image002.jpg")
The DataSource module would use the SnmpProbe ProbeAction mo=
dule
to walk the table and get the index column. Walk config is set to true and a new config called WalkReturnMultipleItems is set to=
true.
This results in reading the index column of the table and returning each in=
dex
as a separate dataItem. Thus, the existing datamapper is able to create ent=
ities
for each returned dataItem:
![](3D"SNMPBasedMonitoring-DiscoveryDevicecomponents_files/image004.jpg")
2. Create another composite DataSource module=
that
would populate the remaining properties of the component instances:
![](3D"SNMPBasedMonitoring-DiscoveryDevicecomponents_files/image006.jpg")
The DataSource module could use the SnmpProbe ProbeAction mo=
dule
to pull out other columns of each table entry, and the ClassSnapshotDataMap=
per ConditionDetection
module to populate the corresponding component instance:<=
/p>
![](3D"SNMPBasedMonitoring-DiscoveryDevicecomponents_files/image008.jpg")
3. Create a discovery rule that uses SNMP walk
DataSource above, targeted at the Device. Please note that it is assumed th=
at
the device would have been already discovered as a NetworkDevice using the =
OOB
SNMP functionality. In the example below, the rPDUOutletConfigIndex column =
of
the rPDUOutletConfigTable table of an APC RackPDU is discovered, and used to
populate the OutletIndex property
![](3D"SNMPBasedMonitoring-DiscoveryDevicecomponents_files/image010.jpg")
4. Once the component instances are created w=
ith
the index property populated, the remaining properties could be populated u=
sing
a Discovery rule targeted at the component type:
![](3D"SNMPBasedMonitoring-DiscoveryDevicecomponents_files/image012.jpg")
Sample MPs
- =
Download
APC RackPDU SNMP Sample MP
- =
Download Network Device with Interfaces (Basic) MP
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