SNMP. Simple Network Management Protocol Philippines Network Operators Group, March Jonathan Brewer Telco2 Limited New Zealand

Transcription

1 SNMP Simple Network Management Protocol Philippines Network Operators Group, March 2018 Jonathan Brewer Telco2 Limited New Zealand

2 Objectives Participants will understand the basics of: SNMP Architecture SNMP Versions SMI and MIBs SNMP Operations SNMPv3 Terminology Common SNMP Tools

3 What is SNMP? The Simple Network Management Protocol is a protocol used to communicate management information between the network management stations and the agents in the network elements. 1 Even though SNMP is a protocol, we use the term SNMP to describe the complete architecutre of the management system. 1 Mauro & Schmidt, Essential SNMP

4 Basics: Network Management Stations Also known as Managers, Network Management Stations execute management applications which monitor and control network elements. 1 1 Mauro & Schmidt, Essential SNMP

5 Basics: Network Elements Elements are devices such as hosts, gateways, terminal servers, and the like, which have management agents responsible for performing the network management functions requested by the network management stations. 1 1 Mauro & Schmidt, Essential SNMP

6 Basics: Agents The agent is a piece of software that runs on the network devices you are managing. It can be a separate program, or it can be incorporated into the operating system. 1 Agents listen and respond on UDP port Mauro & Schmidt, Essential SNMP

7 Basics: SNMP Poll A poll, in the context of network management, is the act of querying an agent for some piece of information. 1 SNMP Managers use UDP to poll agents. 1 Mauro & Schmidt, Essential SNMP

8 Basics: SNMP Trap A trap is a way for the agent to tell the NMS that something has hap- pened. Traps are sent asynchronously, not in response to queries from the NMS. 1 SNMP traps are sent using UDP port Mauro & Schmidt, Essential SNMP

9 Basics: MIB The Management Information Base (MIB) is like a database of managed objects that the agent tracks. Any sort of status or statistical information accessed by the NMS is defined in a MIB. Managed Objects can include Interface Counters, Fan Speeds, System Temperatures, etc.

10 Basics: OID Object Identifier, or the name of a management object. OIDs are globally unique.

11 Basics: Community String In SNMP versions 2c and 3, Community Strings are essentially passwords that control how and what Network Management Stations can access from an Agent.

12 Basics: Protocol Data Unit The PDU is the message format used by Managers and Agents to send and receive information. There are PDUs for all common SNMP operations.

13 SNMPv1 / RFC 1157 (1998) Historic standard but still implemented by many devices Communities are password-like strings that control activities Interactions can be read only, read-write, or trap Traps are event-based messages from an Agent to a Manager 32 bit counters

14 SNMPv2c / RFCs 3416, 3417, & 3418 Adds acknowledged inform messages 64 bit counters available Most commonly used SNMP

15 SNMPv3 / RFCs 2576 & , 3826 Adds authentication and encryption noauthnopriv, authnopriv, authpriv modes Available since 2002, AES since 2004 Not yet widely implemented Please for all new networks!

16 The Structure of Management Information (SMI) Specified by RFCs 1155 & 2578 How objects and their behaviours are defined All information has three attributes Name or Object Identifier (OID) Type & Syntax (defined by Abstract Syntax Notation One) Encoding

17 SMI Heirarchy

18 The Naming of OIDs iso.org.dod.internet.mgmt.mib-2.system.syslocation STRING: Manila, Philippines

19 The "Standard" MIB MIB-II* (RFC 1213) All agents implement MIB-II Defines basic objects incuding basic interface statistics location & contact details

20 SNMP Operation SNMP v1 can perform several operations, including: get getnext set getresponse trap SNMPv2 & SNMPv3 further support: getbulk notification inform report

21 SNMP Get Get is an operation performed by the Manager It's a single query to an Agent for one piece of information The Agent can respond to or drop the request (if it's busy)

22 SNMP GetNext GetNext is an operation performed by the Manager It's a sequence of commands to an Agent for multiple pieces of information GetNext traverses a MIB subtree in order GetNext ends when the Agent responds with an error (end of MIB) SNMPWalk is a tool that implements GetNext

23 SNMP Set Set is an operation performend by the Manager It's used to change the value of a managed object Set can update both read and read-write values Use Set to define a host's name or contact details

24 SNMP Traps SNMP Traps are messages initiated by an Agent Traps are unacknowledged UDP messages Several Generic Traps are defined ColdStart (0), WarmStart (1), linkdown (2), linkup (3), authenticationfailure (4), egpneighbourloss (5), enterprisespecific (6) Vendors & Users must define any enterprisespecific traps

25 SNMP Notification An updated version of SNMP traps Defined in SNMPv2 Harmonises PDU format of traps to that of get / set

26 SNMP Inform An acknowledged Notification Agent is alerted when a Manager has received its message

27 SNMPv3 Protocol remains unchanged Authentication & Encryption are added Terminology & Architecture changes significantly SNMPv3 Terminology Command Generator New Term for Manager Command Responder New Term for Agent Notification Originator An Agent that sends a Trap Notification Receiver A Manager Configured to Receive a Trap Proxy Forwarder Passes Messages Between Entities

28 SNMPv3 Basics: Username Username is a text string representing the account responsible for the SNMP entity to be managed

29 SNMPv3 Basics: Security Level noauthnopriv: No Authentication and No Privacy (like SNMPv1) AuthNoPriv: Authentication Without Privacy AuthPriv: Authentication With Privacy

30 SNMPv3 Basics: Authentication Protocol The protocol used for authentication. SHA1 and MD5 are specified by the RFCs.

31 Authentication Passphrase A password, with a minimum of eight charachters.

32 Privacy Protocol The protocol used for encryption of SNMP packets. AES and DES are specified by the RFCs.

33 Privacy Passphrase The passphrase used with the privacy protocol.

34 SNMP Applications Cricket LibreNMS MRTG PRTG

35 Beyond SNMP 2 SNMP is a heavy-weight protocol with low information density SNMP was not designed for streaming high resolution data It's seen as too slow, incomplete, network-specific, & hard to operationalize New protocols are being developed to stream telemetry data in real-time. Yang data models XML, JSON, and GBP encoding Data pushed from Agents, not requested from Managers UDP, TCP, or grpc transport available 2 Rada Stanic, Model Driven Telemetry - Foundation for Big Data Analytics

36 SNMP Simple Network Management Protocol Philippines Network Operators Group, March 2018 Jonathan Brewer Telco2 Limited New Zealand