Use gRPC Protocol to Define Network Operations with Data Models

XR devices ship with the YANG files that define the data models they support. Using a management protocol such as NETCONF or gRPC, you can programmatically query a device for the list of models it supports and retrieve the model files.

gRPC is an open-source RPC framework. It is based on Protocol Buffers (Protobuf), which is an open source binary serialization protocol. gRPC provides a flexible, efficient, automated mechanism for serializing structured data, like XML, but is smaller and simpler to use. You define the structure using protocol buffer message types in .proto files. Each protocol buffer message is a small logical record of information, containing a series of name-value pairs.

gRPC encodes requests and responses in binary. gRPC is extensible to other content types along with Protobuf. The Protobuf binary data object in gRPC is transported over HTTP/2.

gRPC supports distributed applications and services between a client and server. gRPC provides the infrastructure to build a device management service to exchange configuration and operational data between a client and a server. The structure of the data is defined by YANG models.


Note

All 64-bit IOS XR platforms support gRPC and TCP protocols. All 32-bit IOS XR platforms support only TCP protocol.

Cisco gRPC IDL uses the protocol buffers interface definition language (IDL) to define service methods, and define parameters and return types as protocol buffer message types. The gRPC requests are encoded and sent to the router using JSON. Clients can invoke the RPC calls defined in the IDL to program the router.

The following example shows the syntax of the proto file for a gRPC configuration: 
syntax = "proto3";
 
package IOSXRExtensibleManagabilityService;
 
service gRPCConfigOper {
 
    rpc GetConfig(ConfigGetArgs) returns(stream ConfigGetReply) {};
  
    rpc MergeConfig(ConfigArgs) returns(ConfigReply) {};
 
    rpc DeleteConfig(ConfigArgs) returns(ConfigReply) {};
 
    rpc ReplaceConfig(ConfigArgs) returns(ConfigReply) {};
 
    rpc CliConfig(CliConfigArgs) returns(CliConfigReply) {};
 
    rpc GetOper(GetOperArgs) returns(stream GetOperReply) {};
 
    rpc CommitReplace(CommitReplaceArgs) returns(CommitReplaceReply) {};
} 
message ConfigGetArgs {
     int64 ReqId = 1;
     string yangpathjson = 2;
}
 
message ConfigGetReply {
    int64 ResReqId = 1;
    string yangjson = 2;
    string errors = 3;
}
 
message GetOperArgs {
     int64 ReqId = 1;
     string yangpathjson = 2;
}
 
message GetOperReply {
    int64 ResReqId = 1;
    string yangjson = 2;
    string errors = 3;
}
 
message ConfigArgs {
    int64 ReqId = 1;
    string yangjson = 2;
 
}
 
message ConfigReply {
    int64 ResReqId = 1;
    string errors = 2;
}
 
message CliConfigArgs {
    int64 ReqId = 1;
    string cli = 2;
}
 
message CliConfigReply {
    int64 ResReqId = 1;
    string errors = 2;
}

message CommitReplaceArgs {
     int64 ReqId = 1;
     string cli = 2;
     string yangjson = 3;
}

message CommitReplaceReply {
     int64 ResReqId = 1;
     string errors = 2;
}
Example for gRPCExec configuration:

service gRPCExec {
    rpc ShowCmdTextOutput(ShowCmdArgs) returns(stream ShowCmdTextReply) {};
    rpc ShowCmdJSONOutput(ShowCmdArgs) returns(stream ShowCmdJSONReply) {};
    
}

message ShowCmdArgs {
     int64 ReqId = 1;
     string cli = 2;
}
 
message ShowCmdTextReply {
    int64 ResReqId =1;
    string output = 2;
    string errors = 3;
}
Example for OpenConfiggRPC configuration:
service OpenConfiggRPC {
     rpc SubscribeTelemetry(SubscribeRequest) returns (stream SubscribeResponse) {};
     rpc UnSubscribeTelemetry(CancelSubscribeReq) returns (SubscribeResponse) {};
     rpc GetModels(GetModelsInput) returns (GetModelsOutput) {};
}

message GetModelsInput {
     uint64  requestId   = 1;
     string  name        = 2;
    string  namespace   = 3;
    string  version     = 4;
    enum MODLE_REQUEST_TYPE {
         SUMMARY = 0;
         DETAIL  = 1;
     }
     MODLE_REQUEST_TYPE requestType = 5;
}

message GetModelsOutput {
     uint64  requestId   = 1;
     message ModelInfo {
         string  name        = 1;
         string  namespace   = 2;
        string  version     = 3;
         GET_MODEL_TYPE  modelType = 4;
         string modelData = 5;
     }
     repeated ModelInfo models = 2;
     OC_RPC_RESPONSE_TYPE responseCode = 3;
     string msg = 4;
}

This article describes, with a use case to configure interfaces on a router, how data models helps in a faster programmatic and standards-based configuration of a network, as comapared to CLI.

gRPC Operations

The following are the defined manageability service gRPC operations for Cisco IOS XR:

gRPC Operation

Description

GetConfig

Retrieves the configuration from the router.

GetModels

Gets the supported Yang models on the router

MergeConfig

Merges the input config with the existing device configuration.

DeleteConfig

Deletes one or more subtrees or leaves of configuration.

ReplaceConfig

Replaces part of the existing configuration with the input configuration.

CommitReplace

Replaces all existing configuration with the new configuration provided.

GetOper

Retrieves operational data.

CliConfig

Invokes the input CLI configuration.

ShowCmdTextOutput

Returns the output of a show command in the text form

ShowCmdJSONOutput

Returns the output of a show command in JSON form.

gRPC Operation to Get Configuration

This example shows how a gRPC GetConfig request works for CDP feature.

The client initiates a message to get the current configuration of CDP running on the router. The router responds with the current CDP configuration.

gRPC Request (Client to Router)

gRPC Response (Router to Client) 

 
rpc GetConfig
  {
   "Cisco-IOS-XR-cdp-cfg:cdp": [
    "cdp": "running-configuration"
    ]
  }
 
rpc GetConfig
  {
   "Cisco-IOS-XR-ethernet-lldp-cfg:lldp": [
    "lldp": "running-configuration"
    ]
  }
 

{
 "Cisco-IOS-XR-cdp-cfg:cdp": {
  "timer": 50,
  "enable": true,
  "log-adjacency": [
   null
  ],
  "hold-time": 180,
  "advertise-v1-only": [
   null
  ]
 }
}
{
"Cisco-IOS-XR-ethernet-lldp-cfg:lldp": {
  "timer": 60,
  "enable": true,
  "reinit": 3,
  "holdtime": 150
}
}

gRPC Network Management Interface

gRPC Network Management Interface (gNMI) is a gRPC-based network management protocol used to modify, install or delete configuration from network devices. It is also used to view operational data, control and generate telemetry streams from a target device to a data collection system. It uses a single protocol to manage configurations and stream telemetry data from network devices.

The subscription in a gNMI does not require prior sensor path configuration on the target device. Sensor paths are requested by the collector (such as pipeline), and the subscription mode can be specified for each path. gNMI uses gRPC as the transport protocol and the configuration is same as that of gRPC.

gRPC Network Operations Interface

gRPC Network Operations Interface (gNOI) defines a set of gRPC-based microservices for executing operational commands on network devices. These services are to be used in conjunction with gRPC network management interface (gNMI) for all target state and operational state of a network. gNOI uses gRPC as the transport protocol and the configuration is same as that of gRPC. For more information about gNOI, see the Github repository.

gRPC Authentication Modes

gRPC supports the following authentication modes to secure communication between clients and servers. These authentication modes help ensure that only authorized entities can access the gRPC services, like gNOI, gRIBI, and P4RT. Upon receiving a gRPC request, the device will authenticate the user and perform various authorization checks to validate the user.

The following table lists the authentication type and configuration requirements:

Table 1. gRPC Authentication Modes and Configuration Requirements
Type

Authentication Method

Authorization Method

Configuration Requirement

Requirement From Client

Metadata with TLS

username, password

username

grpc

username, password, and CA

Metadata without TLS

username, password

username

grpc no-tls

username, password

Metadata with Mutual TLS

username, password

username

grpc tls-mutual

username, password, client certificate, client key, and CA

Certificate based Authentication

client certificate's common name field

username from client certificate's common name field

grpc tls-mutual

and

grpc certificate authentication

client certificate, client key, and CA

Certificate based Authentication

In Extensible Manageability Services (EMS) gRPC, the certificates play a vital role in ensuring secure and authenticated communication. The EMS gRPC utilizes the following certificates for authentication:
/misc/config/grpc/ems.pem
/misc/config/grpc/ems.key
/misc/config/grpc/ca.cert

Note

For clients to use the certificates, ensure to copy the certificates from /misc/config/grpc/

Generation of Certificates

These certificates are typically generated using a Certificate Authority (CA) by the device. The EMS certificates, including the server certificate (ems.pem ), public key (ems.key ), and CA certificate (ca.cert ), are generated with specific parameters like the common name ems.cisco.com to uniquely identify the EMS server and placed in the /misc/config/grpc/ location.

The default certificates that are generated by the server are Server-only TLS certificates and by using these certificates you can authenticate the identity of the server.

Usage of Certificates

These certificates are used for enabling secure communication through Transport Layer Security (TLS) between gRPC clients and the EMS server. The client should use ems.pem and ca.cert to initiate the TLS authentication.

To update the certificates, ensure to copy the new certificates that has been generated earlier to the location and restart the server.

Custom Certificates

If you want to use your own certificates for EMS gRPC communication, then you can follow a workflow to generate a custom certificates with the required parameters and then configure the EMS server to use these custom certificates. This process involves replacing the default EMS certificates with the custom ones and ensuring that the gRPC clients also trust the custom CA certificate. For more information on how to customize the common-name , see Certificate Common-Name For Dial-in Using gRPC Protocol.

Certificate Common-Name For Dial-in Using gRPC Protocol

Table 2. Feature History Table

Feature Name

Release Information

Description

Certificate Common-Name For Dial-in Using gRPC Protocol

Release 24.1.1

You can now specify a common-name for the certificate generated by the router while using gRPC dial-in. Earlier, the common-name in the certificate was fixed as ems.cisco.com and was not configurable. Using a specified common-name avoids potential certification failures where you may specify a hostname different from the fixed common name to connect to the router.

The feature introduces these changes:

CLI:

YANG Data Model:

  • New XPath for Cisco-IOS-XR-um-grpc-cfg.yang

  • New XPath for Cisco-IOS-XR-man-ems-cfg

(see GitHub, YANG Data Models Navigator)

When using gRPC dial-in on Cisco IOS-XR router, the common-name associated with the certificate generated by the router is fixed as ems.cisco.com and this caused failure during certificate verification.

From Cisco IOS XR Release 24.1.1, you can now have the flexibility of specifying the common-name in the certificate using the grpc certifcate common-name command. This allows gRPC clients to verify if the domain name in the certificate matches the domain name of the gRPC server being accessed.

Configure Certificate Common Name For Dial-in

Configure a common name to be used in EMSD certificates for gRPC dial-in.

Procedure

Step 1

Configure a common name.

Example:

Router#config
Router(config)#grpc
Router(config-grpc)#certificate common-name cisco.com
Router(config-grpc)#commit

Use the show command to verify the common name:

Router#show grpc	
Certificate common name                 : cisco.com

Note

 

For the above configuration to be successful, ensure to regenerate the certificate. so that the new EMSD certificates include the configured common name.

To regenerate the self-signed certificate, perform the following steps.

Step 2

Remove the certificates: /misc/config/grpc/ems.pem, /misc/config/grpc/ems.key, and /misc/config/grpc/ca.cert from /misc/config/grpc file.

Example:

Router#run ls -ltr /misc/config/grpc/

total 16
drwx------. 2 root root 4096 Feb 14 09:17 dialout
-rw-rw-rw-. 1 root root 1505 Feb 14 10:58 ems.pem
-rw-------. 1 root root 1675 Feb 14 10:58 ems.key
-rw-r--r--. 1 root root 1505 Feb 14 10:58 ca.cert
Router#run rm -rf /misc/config/grpc/ems.pem /misc/config/grpc/ems.key
Router#run ls -ltr /misc/config/grpc/

total 8
drwx------. 2 root root 4096 Feb 14 09:17 dialout
-rw-r--r--. 1 root root 1505 Feb 14 10:58 ca.cert

Step 3

Restart gRPC server by toggling the TLS configuration.

Configure gRPC with non TLS and then re-configure with TLS.

Example:

Router#config
Router(config)#grpc
Router(config-grpc)#no-tls
Router(config-grpc)#commit
Router#run ls -ltr /misc/config/grpc/

total 8
drwx------. 2 root root 4096 Feb 14 09:17 dialout
-rw-r--r--. 1 root root 1505 Feb 14 10:58 ca.cert
Router#config                        
Router(config)#grpc
Router(config-grpc)#no no-tls
Router(config-grpc)#commit
Router#run ls -ltr /misc/config/grpc/

total 16
drwx------. 2 root root 4096 Feb 14 09:17 dialout
-rw-rw-rw-. 1 root root 1505 Feb 14 14:23 ems.pem
-rw-------. 1 root root 1675 Feb 14 14:23 ems.key
-rw-r--r--. 1 root root 1505 Feb 14 14:23 ca.cert

Copy the newly generated /misc/config/grpc/ems.pem certificate in this path (from the device) to the gRPC client.

Configure Interfaces Using Data Models in a gRPC Session

Google-defined remote procedure call () is an open-source RPC framework. gRPC supports IPv4 and IPv6 address families. The client applications use this protocol to request information from the router, and make configuration changes to the router.

The process for using data models involves:

  • Obtain the data models.

  • Establish a connection between the router and the client using gRPC communication protocol.

  • Manage the configuration of the router from the client using data models.


Note

Configure AAA authorization to restrict users from uncontrolled access. If AAA authorization is not configured, the command and data rules associated to the groups that are assigned to the user are bypassed. An IOS-XR user can have full read-write access to the IOS-XR configuration through Network Configuration Protocol (NETCONF), google-defined Remote Procedure Calls (gRPC) or any YANG-based agents. In order to avoid granting uncontrolled access, enable AAA authorization using aaa authorization exec command before setting up any configuration. For more information about configuring AAA authorization, see the System Security Configuration Guide.

In this section, you use native data models to configure loopback and ethernet interfaces on a router using a gRPC session.

Consider a network topology with four routers and one controller. The network consists of label edge routers (LER) and label switching routers (LSR). Two routers LER1 and LER2 are label edge routers, and two routers LSR1 and LSR2 are label switching routers. A host is the controller with a gRPC client. The controller communicates with all routers through an out-of-band network. All routers except LER1 are pre-configured with proper IP addressing and routing behavior. Interfaces between routers have a point-to-point configuration with /31 addressing. Loopback prefixes use the format 172.16.255.x/32.

The following image illustrates the network topology:
Figure 1. Network Topology for gRPC session

You use Cisco IOS XR native model Cisco-IOS-XR-ifmgr-cfg.yang to programmatically configure router LER1.

Before you begin

  • Retrieve the list of YANG modules on the router using NETCONF monitoring RPC. For more information

  • Configure Transport Layer Security (TLS). Enabling gRPC protocol uses the default HTTP/2 transport with no TLS. gRPC mandates AAA authentication and authorization for all gRPC requests. If TLS is not configured, the authentication credentials are transferred over the network unencrypted. Enabling TLS ensures that the credentials are secure and encrypted. Non-TLS mode can only be used in secure internal network.

Procedure

Step 1

Enable gRPC Protocol

To configure network devices and view operational data, gRPC proptocol must be enabled on the server. In this example, you enable gRPC protocol on LER1, the server.

Note

 

Cisco IOS XR 64-bit platforms support gRPC protocol. The 32-bit platforms do not support gRPC protocol.

  1. Enable gRPC over an HTTP/2 connection.

    Example:

    
Router#configure
Router(config)#grpc
Router(config-grpc)#port <port-number>

    The port number ranges from 57344 to 57999. If a port number is unavailable, an error is displayed.

  2. Set the session parameters.

    Example:

    Router(config)#grpc {address-family | certificate-authentication | dscp | max-concurrent-streams | max-request-per-user | max-request-total | max-streams | 
max-streams-per-user | no-tls | tlsv1-disable | tls-cipher | tls-mutual | tls-trustpoint | service-layer | vrf}

    where:

    • address-family: set the address family identifier type.

    • certificate-authentication: enables certificate based authentication

    • dscp: set QoS marking DSCP on transmitted gRPC.

    • max-request-per-user: set the maximum concurrent requests per user.

    • max-request-total: set the maximum concurrent requests in total.

    • max-streams: set the maximum number of concurrent gRPC requests. The maximum subscription limit is 128 requests. The default is 32 requests.

    • max-streams-per-user: set the maximum concurrent gRPC requests for each user. The maximum subscription limit is 128 requests. The default is 32 requests.

    • no-tls: disable transport layer security (TLS). The TLS is enabled by default

    • tlsv1-disable: disable TLS version 1.0

    • service-layer: enable the grpc service layer configuration.

      This parameter is not supported in Cisco ASR 9000 Series Routers, Cisco NCS560 Series Routers, , and Cisco NCS540 Series Routers.

    • tls-cipher: enable the gRPC TLS cipher suites.

    • tls-mutual: set the mutual authentication.

    • tls-trustpoint: configure trustpoint.

    • server-vrf: enable server vrf.

    After gRPC is enabled, use the YANG data models to manage network configurations.

Step 2

Configure the interfaces.

In this example, you configure interfaces using Cisco IOS XR native model Cisco-IOS-XR-ifmgr-cfg.yang. You gain an understanding about the various gRPC operations while you configure the interface. For the complete list of operations, see gRPC Operations. In this example, you merge configurations with merge-config RPC, retreive operational statistics using get-oper RPC, and delete a configuration using delete-config RPC. You can explore the structure of the data model using YANG validator tools such as pyang.

LER1 is the gRPC server, and a command line utility grpcc is used as a client on the controller. This utility does not support YANG and, therefore, does not validate the data model. The server, LER1, validates the data mode.

Note

 

The OC interface maps all IP configurations for parent interface under a VLAN with index 0. Hence, do not configure a sub interface with tag 0.

  1. Explore the XR configuration model for interfaces and its IPv4 augmentation.

    Example:

    
controller:grpc$ pyang --format tree --tree-depth 3 Cisco-IOS-XR-ifmgr-cfg.yang
Cisco-IOS-XR-ipv4-io-cfg.yang 
module: Cisco-IOS-XR-ifmgr-cfg 
    +--rw global-interface-configuration 
    | +--rw link-status? Link-status-enum 
    +--rw interface-configurations 
        +--rw interface-configuration* [active interface-name] 
            +--rw dampening 
            | ... 
            +--rw mtus 
            | ... 
            +--rw encapsulation 
            | ... 
            +--rw shutdown? empty 
            +--rw interface-virtual? empty 
            +--rw secondary-admin-state? Secondary-admin-state-enum 
            +--rw interface-mode-non-physical? Interface-mode-enum 
            +--rw bandwidth? uint32 
            +--rw link-status? empty 
            +--rw description? string 
            +--rw active Interface-active 
            +--rw interface-name xr:Interface-name 
            +--rw ipv4-io-cfg:ipv4-network 
            | ... 
            +--rw ipv4-io-cfg:ipv4-network-forwarding ...

  2. Configure a loopback0 interface on LER1.

    Example:

    controller:grpc$ more xr-interfaces-lo0-cfg.json 
{ 
 "Cisco-IOS-XR-ifmgr-cfg:interface-configurations": 
  { "interface-configuration": [ 
    { 
      "active": "act", 
      "interface-name": "Loopback0", 
      "description": "LOCAL TERMINATION ADDRESS", 
      "interface-virtual": [ 
        null 
       ], 
       "Cisco-IOS-XR-ipv4-io-cfg:ipv4-network": { 
        "addresses": { 
            "primary": { 
              "address": "172.16.255.1", 
              "netmask": "255.255.255.255" 
       } 
      } 
     } 
    } 
   ] 
 } 
}

  3. Merge the configuration.

    Example:

    
controller:grpc$ grpcc -username admin -password admin -oper merge-config 
-server_addr 198.18.1.11:57400 -json_in_file xr-interfaces-gi0-cfg.json 
emsMergeConfig: Sending ReqId 1 
emsMergeConfig: Received ReqId 1, Response ' 
'

  4. Configure the ethernet interface on LER1.

    Example:

    
controller:grpc$ more xr-interfaces-gi0-cfg.json 
{ 
 "Cisco-IOS-XR-ifmgr-cfg:interface-configurations": { 
   "interface-configuration": [ 
    { 
     "active": "act", 
     "interface-name": "GigabitEthernet0/0/0/0", 
     "description": "CONNECTS TO LSR1 (g0/0/0/0)", 
     "Cisco-IOS-XR-ipv4-io-cfg:ipv4-network": { 
        "addresses": { 
         "primary": { 
            "address": "172.16.1.0", 
            "netmask": "255.255.255.254" 
      } 
     } 
    } 
   } 
  ] 
 } 
}

  5. Merge the configuration.

    Example:

    
controller:grpc$ grpcc -username admin -password admin -oper merge-config 
-server_addr 198.18.1.11:57400 -json_in_file xr-interfaces-gi0-cfg.json 
emsMergeConfig: Sending ReqId 1 
emsMergeConfig: Received ReqId 1, Response ' 
'

  6. Enable the ethernet interface GigabitEthernet 0/0/0/0 on LER1 to bring up the interface. To do this, delete shutdown configuration for the interface.

    Example:

    
controller:grpc$ grpcc -username admin -password admin -oper delete-config 
-server_addr 198.18.1.11:57400 -yang_path "$(< xr-interfaces-gi0-shutdown-cfg.json )" 
emsDeleteConfig: Sending ReqId 1, yangJson { 
 "Cisco-IOS-XR-ifmgr-cfg:interface-configurations": { 
   "interface-configuration": [ 
   { 
    "active": "act", 
    "interface-name": "GigabitEthernet0/0/0/0", 
    "shutdown": [ 
      null 
    ] 
   } 
  ] 
 } 
} 
emsDeleteConfig: Received ReqId 1, Response ''

Step 3

Verify that the loopback interface and the ethernet interface on router LER1 are operational.

Example:


controller:grpc$ grpcc -username admin -password admin -oper get-oper 
-server_addr 198.18.1.11:57400 -oper_yang_path "$(< xr-interfaces-briefs-oper-filter.json )" 
emsGetOper: Sending ReqId 1, yangPath { 
  "Cisco-IOS-XR-pfi-im-cmd-oper:interfaces": { 
    "interface-briefs": [ 
      null 
     ] 
  } 
}
{ "Cisco-IOS-XR-pfi-im-cmd-oper:interfaces": { 
  "interface-briefs": { 
    "interface-brief": [ 
    { 
      "interface-name": "GigabitEthernet0/0/0/0", 
      "interface": "GigabitEthernet0/0/0/0", 
      "type": "IFT_GETHERNET", 
      "state": "im-state-up", 
      "actual-state": "im-state-up", 
      "line-state": "im-state-up", 
      "actual-line-state": "im-state-up", 
      "encapsulation": "ether", 
      "encapsulation-type-string": "ARPA", 
      "mtu": 1514, 
      "sub-interface-mtu-overhead": 0, 
      "l2-transport": false, 
      "bandwidth": 1000000 
     },
     { 
      "interface-name": "GigabitEthernet0/0/0/1", 
      "interface": "GigabitEthernet0/0/0/1", 
      "type": "IFT_GETHERNET", 
      "state": "im-state-up", 
      "actual-state": "im-state-up", 
      "line-state": "im-state-up", 
      "actual-line-state": "im-state-up", 
      "encapsulation": "ether", 
      "encapsulation-type-string": "ARPA", 
      "mtu": 1514, 
      "sub-interface-mtu-overhead": 0, 
      "l2-transport": false, 
      "bandwidth": 1000000 
     },
     { 
      "interface-name": "Loopback0", 
      "interface": "Loopback0", 
      "type": "IFT_LOOPBACK", 
      "state": "im-state-up", 
      "actual-state": "im-state-up", 
      "line-state": "im-state-up", 
      "actual-line-state": "im-state-up", 
      "encapsulation": "loopback", 
      "encapsulation-type-string": "Loopback", 
      "mtu": 1500, 
      "sub-interface-mtu-overhead": 0, 
      "l2-transport": false, 
      "bandwidth": 0 
   },
   { 
      "interface-name": "MgmtEth0/RP0/CPU0/0", 
      "interface": "MgmtEth0/RP0/CPU0/0", 
      "type": "IFT_ETHERNET", 
      "state": "im-state-up", 
      "actual-state": "im-state-up", 
      "line-state": "im-state-up", 
      "actual-line-state": "im-state-up", 
      "encapsulation": "ether", 
      "encapsulation-type-string": "ARPA", 
      "mtu": 1514, 
      "sub-interface-mtu-overhead": 0, 
      "l2-transport": false, 
      "bandwidth": 1000000 
   },
   { 
      "interface-name": "Null0", 
      "interface": "Null0", 
      "type": "IFT_NULL", 
      "state": "im-state-up", 
      "actual-state": "im-state-up", 
      "line-state": "im-state-up", 
      "actual-line-state": "im-state-up", 
      "encapsulation": "null", 
      "encapsulation-type-string": "Null", 
      "mtu": 1500, 
      "sub-interface-mtu-overhead": 0, 
      "l2-transport": false, 
      "bandwidth": 0 
    } 
   ] 
  } 
 } 
} 
emsGetOper: ReqId 1, byteRecv: 2325

In summary, router LER1, which had minimal configuration, is now programmatically configured using data models with an ethernet interface and is assigned a loopback address. Both these interfaces are operational and ready for network provisioning operations.