Telemetry Configuration Guide for Cisco 8000 Series Routers, IOS XR Releases

Telemetry session establishment methods

Updated: June 9, 2026

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Lists the available methods for establishing a telemetry session, including dial-out and dial-in modes.

This reference outlines the methods for establishing a telemetry session and highlights their similarities.

You can initiate a telemetry session using dial-out mode or dial-in mode. Both modes use the same data model and stream the same data.

Dial-out mode: The device initiates the connection to the collector.
Dial-in mode: The collector initiates the connection to the device.

Table 1. Telemetry session establishment methods comparison
Method	Initiator	Data Model	Data Streamed
Dial-out	Device	Same	Same
Dial-in	Collector	Same	Same

Dial-out mode

Dial-out mode is a configuration mode that enables the router to initiate a subscription-based telemetry session by connecting to the receiver.

Because the router starts the connection, you do not need to manage ports for inbound traffic.
A simple protocol requires only access to the socket on the collector, while a secure protocol provides authentication and encryption for the session.
This allows you to secure your collector and use a more advanced communication method with the router.

Dial-out mode operation and protocol options

Dial-out mode enables the router to initiate a connection to the receiver, establishing a subscription-based telemetry session. The router starts the connection, eliminating the need to manage ports for inbound traffic. This default mode lets you choose between protocols that offer simplicity, such as TCP, or security, such as gRPC. Simple protocols require only access to the socket on the collector, while secure protocols provide authentication and encryption for the session. This secures your collector and enables advanced communication with the router. If the connection between the router and the destination is lost, the router re-establishes the connection and continues to push data. Data transmitted during the reconnection period is lost.

For information about creating a dial-out session, refer to Establish a Model-Driven Telemetry Session from a Router to a Collector.

Dial-in mode

Dial-in mode is a configuration mode that enables a collector to initiate a connection to the router and dynamically subscribe to sensor paths for data collection.

Because the collector establishes the session, destinations do not need to be created in the router configuration.
The protocol used to establish the session, gRPC, provides advanced security capabilities to authenticate and encrypt the session.
Only gRPC supports dial-in sessions.

Dial-in mode operation and session behavior

Dial-in mode allows a collector to initiate a connection to the router and subscribe dynamically to one or more sensor paths specified in a subscription. The router accepts connections from the collector, enabling a single channel of communication. Because the collector establishes the session, destinations do not need to be created in the router configuration. The protocol used to establish the session, gRPC, provides advanced security capabilities to authenticate and encrypt the session. If the connection between the router and the collector is lost, the session is cancelled, and the collector must reconnect to the router to restart data streaming. Only gRPC supports dial-in sessions.

To explore dial-in mode and create a dial-in session, refer to Model-driven telemetry sessions.

Dial-in mode offers several operational characteristics:

The collector initiates the session, eliminating the need for destination configuration on the router.
gRPC protocol ensures secure authentication and encryption for the session.
Session cancellation occurs if the connection is lost, requiring the collector to reconnect for data streaming.

Dial-in mode session steps:

The collector initiates a connection to the router.
The router accepts the connection and enables communication.
The collector subscribes to sensor paths for data collection.

Dial-in mode attributes and descriptions:

Collector-initiated session: The collector starts the connection.
Dynamic subscription: Sensor paths are subscribed to during the session.
gRPC protocol: Provides authentication and encryption.

Comparison of dial-in mode and other modes:

Table 2. Dial-in mode vs. other modes
Attributes	Dial-in mode	Other modes
Session initiation	Collector initiates	Router initiates
Protocol	gRPC	Other protocols

Contrast between dial-in mode and router-initiated mode:

Table 3. Dial-in vs. router-initiated mode
Dial-in mode	Router-initiated mode
Collector initiates session	Router initiates session

Lookup table for dial-in mode attributes:

Table 4. Dial-in mode attribute lookup
Items	Attribute 1	Attribute 2
Dial-in session	Collector-initiated	gRPC protocol
Router-initiated session	Router-initiated	Other protocols

Note

TIP: Only gRPC supports dial-in sessions, and session security is ensured through authentication and encryption.

Dial-in mode session visual representation:

Dial-in mode example

For example, a collector initiates a gRPC connection to a router, subscribes to sensor paths, and receives streaming telemetry data without configuring destinations on the router.

Dial-in mode counter-example

In router-initiated mode, the router establishes the session and requires destination configuration, which differs from dial-in mode.

Dial-in mode analogy

Dial-in mode is like a guest calling a host to request information, rather than the host reaching out to the guest.

Identify the telemetry session suitable for your network

Identify the appropriate telemetry session mode for your network based on transport protocols, encoding formats, and data streaming needs.

The transport protocols and encoding formats in your network help determine which telemetry session mode is suitable for your needs. Encoding efficiency depends on the space data occupies on the wire, memory utilization, and the amount of data you plan to stream from the router.

Use TCP dial-out mode to stream telemetry data with a simple setup involving a single router and collector. This mode is easy to configure and does not require extensive protocol knowledge. It eliminates the need to manage ports for inbound connections.
Use gRPC dial-out mode if your setup requires scaling to many devices or encrypting your data. This mode also removes the need to manage ports for inbound connections.
Use gRPC dial-in mode if you already use gRPC in your network and want dynamic sessions without streaming data to fixed destinations. This mode is convenient for centralized configuration and operational data requests.

Table 5. Telemetry session modes and attributes
Session Mode	Transport Protocol	Encoding Format	Use Case
TCP dial-out	TCP	GPB/JSON	Simple setup, single router and collector, easy configuration, no inbound port management
gRPC dial-out	gRPC	GPB/JSON	Scalable to many devices, supports encryption, no inbound port management
gRPC dial-in	gRPC	GPB/JSON	Dynamic sessions, centralized configuration, operational data requests, no fixed streaming destinations

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