Network O&M and Troubleshooting · Topic 1 of 3
Network Management with SNMP, NETCONF, RESTCONF and iMaster NCE
Learn network management for H12-811: NMS and agents, SNMP versions, operations and ports, NETCONF and YANG, RESTCONF methods, and iMaster NCE.
- 5 min
- NMS sends requests; the agent on the device answers and sends traps; the MIB holds managed objects.
- SNMP ports: UDP 161 to the agent, UDP 162 to the NMS for traps and informs.
- Only SNMPv3 has authentication and encryption; v1 and v2c use plain-text community names.
What it is
Network management is monitoring, configuring and maintaining network devices so the network stays available and performs well. A management station talks to software on each device, using a management protocol.
SNMP is the classic protocol for monitoring. NETCONF and RESTCONF are model-driven protocols built for configuration and automation. iMaster NCE is Huawei's platform that uses these protocols to manage, control and analyze whole networks.
How it works
Basic concepts of network management
| Term | Meaning |
|---|---|
| NMS (network management system) | The station or software that sends requests and receives alarms |
| Agent | Software on the managed device that answers requests and sends notifications |
| Managed object | Something on the device that can be read or set, such as an interface counter |
| MIB | The database of managed objects that SNMP uses, organized as a tree of OIDs |
The ISO FCAPS model lists five management functions: Fault, Configuration, Accounting, Performance and Security. Management traffic can be in-band (over the service network) or out-of-band (over a separate management port or network).
Traditional management uses the CLI, web pages and SNMP, device by device. Model-driven management uses NETCONF, RESTCONF and YANG, so a controller can configure many devices automatically.
SNMP
| Version | Security | Notes |
|---|---|---|
| SNMPv1 | Community name in plain text | Original version |
| SNMPv2c | Community name in plain text | Adds GetBulk and Inform |
| SNMPv3 | User-based security model (USM): authentication and encryption | Recommended; security levels noAuthNoPriv, authNoPriv, authPriv |
| Operation | Direction | Purpose |
|---|---|---|
| Get, GetNext | NMS to agent | Read one object or the next object in the tree |
| GetBulk (v2c and v3) | NMS to agent | Read many objects in one request |
| Set | NMS to agent | Change an object value |
| Trap | Agent to NMS | Unsolicited alarm, not acknowledged |
| Inform (v2c and v3) | Agent to NMS | Alarm that the NMS acknowledges |
SNMP runs over UDP. The agent listens on UDP 161 for Get and Set; traps and informs go to the NMS on UDP 162. Objects are named by OIDs, for example 1.3.6.1.2.1.1.5.0 is sysName in the standard MIB-2 system group.
A basic SNMPv2c agent on VRP:
[Huawei] snmp-agent
[Huawei] snmp-agent sys-info version v2c
[Huawei] snmp-agent community read cipher Example@123
[Huawei] snmp-agent trap enableNETCONF
NETCONF (RFC 6241) configures devices with XML messages, usually over SSH on TCP port 830. The device data it carries is described by YANG data models.
| NETCONF layer | Contents |
|---|---|
| Content | The configuration and state data, defined by YANG |
| Operations | <get>, <get-config>, <edit-config>, <copy-config>, <delete-config>, <lock>, <unlock>, <close-session>, <kill-session> |
| Messages | <rpc> and <rpc-reply> |
| Secure transport | SSH (most common), TLS |
A session starts with each side sending a <hello> that lists its capabilities. Configuration lives in datastores: <running/>, plus <candidate/> and <startup/> where the device supports them. With a candidate datastore, changes are staged and then committed together.
RESTCONF
RESTCONF (RFC 8040) gives HTTP access to the same YANG-modeled data, over HTTPS. Data can be encoded in XML or JSON, and resources are addressed by URIs under /restconf/data/.
| HTTP method | Maps to |
|---|---|
| GET | Read data, like <get> or <get-config> |
| POST | Create a resource |
| PUT | Create or replace a resource |
| PATCH | Merge changes into a resource |
| DELETE | Delete a resource |
RESTCONF is simpler for web developers, while NETCONF adds features such as locks and the candidate datastore.
Introduction to iMaster NCE
iMaster NCE is Huawei's network automation and intelligence platform. It combines management, control, analysis and AI functions in one system, covering the network lifecycle of planning, building, maintaining and optimizing.
| Interface | Protocols |
|---|---|
| Northbound, to applications and OSS | RESTful APIs |
| Southbound, to network devices | NETCONF, SNMP, telemetry, CLI and others |
Variants serve different networks, for example iMaster NCE-Campus for campus and branch networks, iMaster NCE-Fabric for data center networks and iMaster NCE-WAN for WAN and SD-WAN.
A worked example
An operator wants alarms when a link goes down and wants to push the same VLAN configuration to 200 switches. For alarms, the switches send SNMP traps to the NMS on UDP 162; for secure polling, the operator uses SNMPv3 at authPriv.
For the VLAN change, iMaster NCE-Campus sends a NETCONF <edit-config> over SSH port 830 to each switch. An in-house portal reads the result through iMaster NCE's northbound RESTful API.
How the exam asks about this
- "Which SNMP message does the agent send without a request, and is it acknowledged?" → A Trap, which is not acknowledged; an Inform is acknowledged.
- "Which data modeling language describes NETCONF content?" → YANG.
- "Which RESTCONF method merges changes into an existing resource?" → PATCH.
What to remember for the exam
- NMS sends requests; the agent on the device answers and sends traps; the MIB holds managed objects.
- SNMP ports: UDP 161 to the agent, UDP 162 to the NMS for traps and informs.
- Only SNMPv3 has authentication and encryption; v1 and v2c use plain-text community names.
- NETCONF: XML, RPC messages, SSH port 830, four layers, YANG models, running and candidate datastores.
- RESTCONF: HTTPS, XML or JSON, HTTP methods GET, POST, PUT, PATCH, DELETE.
GetBulk and Inform do not exist in SNMPv1. They were added in SNMPv2c and are kept in SNMPv3.
Common mistakes
Swapping 161 and 162. Requests go to the agent on UDP 161. Traps and informs go to the NMS on UDP 162.
Calling SNMPv2c secure. The "c" means community-based. Community names travel in plain text, exactly as in SNMPv1.
Thinking RESTCONF replaces YANG. RESTCONF and NETCONF are transports and operations. Both use YANG to define the data they carry.
Check yourself
What are the four layers of NETCONF?
Content, operations, messages and secure transport.
Which SNMPv3 security level provides both authentication and encryption?
authPriv.
What do iMaster NCE's northbound interfaces provide?
RESTful APIs that let upper-layer applications and OSS systems use the platform's functions.
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