• Knowledge of YANG is needed to understand and define the data that is required when using telemetry.

• Knowledge of XML, XML namespaces, and XML XPath.

• Knowledge of standards and principles defined by the IETF telemetry specifications.

• The urn:ietf:params:netconf:capability:notification:1.1 capability must be listed in hello messages. This capability is advertised only on devices that support IETF telemetry.

• NETCONF-YANG must be configured and running on the device.

  Note	NETCONF-YANG must be configured for telemetry to work, even if NETCONF is not used. For more information on configuring NETCONF-YANG, see the NETCONF Protocol module.

  Verify that the following processes are running, by using the show platform software yang-management process command :

  
  Device# show platform software yang-management process 
  
  confd : Running 
  nesd : Running 
  syncfd : Running 
  ncsshd : Running 
  dmiauthd : Running 
  nginx : Running 
  ndbmand : Running 
  pubd : Running 
  gnmib : Running 
  
  

  Note	The process pubd is the model-driven telemetry process, and if it is not running, model-driven telemetry will not work.

  The following table provides details about each of the Device Management Interface (DMI) processes.

  Table 1. Field Descriptions

  Device Management Interface Process Name	Primary Role
  confd	Configuration daemon.
  nesd	Network element synchronizer daemon.
  syncfd	Sync daemon (maintains synchronization between the running state and corresponding models).
  ncsshd	NETCONF Secure Shell (SSH) daemon.
  dmiauthd	DMI authentication daemon.
  nginx	NGINX web server. Acts as a web server for RESTCONF.
  ndbmand	NETCONF database manager.
  pubd	Publication manager and publisher used for model-driven telemetry.
  gnmib	GNMI protocol server.

NETCONF-Specific Prerequisites

• Knowledge of NETCONF and how to use it, including:

  • Establishing a NETCONF session.

  • Sending and receiving hello and capabilities messages.

  • Sending and receiving YANG XML RPCs over the established NETCONF session. For more information, see the Configure NETCONF/YANG and Validate Example for Cisco IOS XE 16.x Platforms document.

Enabling and Validating NETCONF

The NETCONF functionality can be verified by creating an SSH connection to the device using a valid username and password and receiving a hello message, which contains the capability of the device:

Device:~ USER1$ ssh -s cisco1@172.16.167.175 -p 830 netconf 
cisco1@172.16.167.175's password: cisco1

<?xml version="1.0" encoding="UTF-8"?>
<hello xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<capabilities>
<capability>urn:ietf:params:netconf:base:1.0</capability>
<capability>urn:ietf:params:netconf:base:1.1</capability>
<capability>urn:ietf:params:netconf:capability:writable-running:1.0</capability>
<capability>urn:ietf:params:netconf:capability:xpath:1.0</capability>
<capability>urn:ietf:params:netconf:capability:validate:1.0</capability>
<capability>urn:ietf:params:netconf:capability:validate:1.1</capability>
<capability>urn:ietf:params:netconf:capability:rollback-on-error:1.0</capability
.
.
.
</capabilities>
<session-id>2870</session-id></hello>]]>]]>

Use < ^C > to exit

NETCONF is ready to use, when a successful reply is received in response to your hello message.

RESTCONF-Specific Prerequisites

• Knowledge of RESTCONF and how to use it (when creating a subscription using RESTCONF).

• RESTCONF must be configured on the device.

• RESTCONF must send correctly-formed Uniform Resource Identifiers (URIs) that adhere to RESTCONF RFC 8040.

Enabling and Validating RESTCONF

Validate RESTCONF using appropriate credentials and the following URI:

Operation: GET
Headers:
"	Accept: application/yang-data.collection+json, application/yang-data+json, application/yang-data.errors+json
"	Content-Type: application/yang-data+json
Returned Output (omitted for breverity): 
{
    "ietf-restconf:data": {
        "ietf-yang-library:modules-state": {
            "module": [
                {
                    "name": "ATM-FORUM-TC-MIB",
                    "revision": "",
                    "schema": "https://10.85.116.28:443/restconf/tailf/modules/ATM-FORUM-TC-MIB",
                    "namespace": "urn:ietf:params:xml:ns:yang:smiv2:ATM-FORUM-TC-MIB"
                },
                {
                    "name": "ATM-MIB",
                    "revision": "1998-10-19",
                    "schema": "https://10.85.116.28:443/restconf/tailf/modules/ATM-MIB/1998-10-19",
                    "namespace": "urn:ietf:params:xml:ns:yang:smiv2:ATM-MIB"
                },
                {
                    "name": "ATM-TC-MIB",
                    "revision": "1998-10-19",
                    "schema": "https://10.85.116.28:443/restconf/tailf/
..
<snip>
..
}

RESTCONF is validated successfully when you receive the above reply with all device capabilities.

gRPC-Specific Prerequisites

• Set up a gRPC collector that understands key-value Google Protocol Buffers (GPB) encoding.

• Automatic hierarchy in selections is not supported for on-change subscriptions when using the yang-push stream. This means that when selecting a list, child lists of the list are not automatically included. For example, the subscriber must manually create a subscription for each child list.

  This restriction also applies to periodic subscriptions, if subscribed to the elements in the list below:

  • Cisco-IOS-XE-wireless-access-point-oper

  • Cisco-IOS-XE-wireless-ap-global-oper

  • Cisco-IOS-XE-wireless-awips-oper

  • Cisco-IOS-XE-wireless-client-global-oper

  • Cisco-IOS-XE-wireless-client-oper

  • Cisco-IOS-XE-wireless-general-cfg

  • Cisco-IOS-XE-wireless-general-oper

  • Cisco-IOS-XE-wireless-mesh-cfg

  • Cisco-IOS-XE-wireless-mesh-oper

  • Cisco-IOS-XE-wireless-mobility-oper

  • Cisco-IOS-XE-wireless-rfid-oper

  • Cisco-IOS-XE-wireless-rrm-emul-oper

  • Cisco-IOS-XE-wireless-rrm-global-oper

  • Cisco-IOS-XE-wireless-rrm-oper

  • Cisco-IOS-XE-wireless-site-cfg

  • bootcamp-test-autonomous

  • openconfig-access-points

  • openconfig-ap-manager

  • openconfig-lacp

  • openconfig-platform-psu

• Checking the authorization of data access is not supported. All the data requested by a subscriber is sent.

• Subtree filters are not supported. If subtree filters are specified, the subscription is marked as invalid.

• Defining multiple receivers within subscription parameters is not supported; only the first receiver destination is attempted. Other defined receivers are ignored.

gRPC-Specific Restrictions

• Transport Layer Security-based (TLS-based) authentication between a device and receiver is not supported.

  TLS-based authentication is supported in Cisco IOS XE Amsterdam 17.1.1 and later releases.

yang-push-Specific Restriction

• Subscription quality of service (QoS) is not supported.