Data Fields example: SNMP

Ever wondered how to provide an easy to use SNMP configuration to your users? That’s what we’re going to show in this example. Once completed, all your Hosts inheriting a specific (or your “default”) Host Template will provide an optional SNMP version field.

In case you choose no version, nothing special will happen. Otherwise, the host offers additional fields depending on the chosen version. Community String for SNMPv1 and SNMPv2c, and five other fields ranging from Authentication User to Auth and Priv types and keys for SNMPv3.

Your services should now be applied not only based on various Host properties like Device Type, Application, Customer or similar - but also based on the fact whether credentials have been given or not.

Prepare required Data Fields

As we already have learned, Fields are what allows us to define which custom variables can or should be defined following which rules. We want SNMP version to be a drop-down, and that’s why we first define a Data List, followed by a Data Field using that list:

Create a new Data List

Fill the new list with SNMP versions

Create a corresponding Data Field

Next, please also create the following elements:

• a list SNMPv3 Auth Types providing MD5 and SHA
• a list SNMPv3 Priv Types providing at least AES and DES
• a String type field snmp_community labelled SNMP Community
• a String type field snmpv3_user labelled SNMPv3 User
• a String type field snmpv3_auth labelled SNMPv3 Auth (authentication key)
• a String type field snmpv3_priv labelled SNMPv3 Priv (encryption key)
• a Data List type field snmpv3_authprot labelled SNMPv3 Auth Type
• a Data List type field snmpv3_privprot labelled SNMPv3 Priv Type

Please do not forget to add meaningful descriptions, telling your users about in-house best practices.

Assign your shiny new Fields to a Template

I’m using my default Host Template for this, but one might also choose to provide SNMP version on Network Devices. Should Network Device be a template? Or just an option in a Device Type field? You see, the possibilities are endless here.

This screenshot shows part of my assigned Fields:

While I kept SNMP Version optional, all other fields are mandatory.

Use your Template

As soon as you choose your template, a new field is shown:

In case you change it to SNMPv2c, a Community String will be required:

Switch it to SNMPv3 to see completely different fields:

Once stored please check the rendered configuration. Switch the SNMP versions forth and back, and you should see that filtered fields will also remove the corresponding values from the object.

Assign Services based on those properties

You should design your Commands to use that set of properties. Change the example slightly to fit ITL Commands in case you’re using those (snmpv3_*_type VS _alg).

Your Cisco Health checks assigned to all:

• routers or switches
• manifactured by Cisco
• with SNMP credentials, regardless of which version

…might then look as follows:

Have fun!