Chapter 23 Simple Network Management Protocol SNMP 1

Chapter 23 Simple Network Management Protocol (SNMP) 1 ©The Mc. Graw-Hill Companies, Inc. , 2000 1 © Adapted for use at JMU by Mohamed Aboutabl, 2003

CONTENTS • • CONCEPT MANAGEMENT COMPONENTS SMI MIB SNMP MESSAGES UDP PORTS SECURITY 2 ©The Mc. Graw-Hill Companies, Inc. , 2000 2 © Adapted for use at JMU by Mohamed Aboutabl, 2003

23. 1 Concept n n n Manager checks Agent’s performance Manager changes Agent’s operating parameters Agent reports warnings to Manager Router/ Switch/ Network Printer running the SNM Server program A PC running the SNMP client program 3 ©The Mc. Graw-Hill Companies, Inc. , 2000 3 © Adapted for use at JMU by Mohamed Aboutabl, 2003

23. 2 Components of network management on the Internet Management Information Base Structure of Management Information n SNMP defines the format of packets exchanged between a manager and an agent. It reads and changes the status (values) of objects (variables) in SNMP packets. SMI defines the general rules for naming objects, defining object types (including range and length), and showing how to encode objects and values. q SMI defines neither the number of objects an entity should manage, nor names the objects to be managed nor defines the association between the objects and their values. MIB creates a collection of named objects, their types, and their relationships to each other in an entity to be managed. 4 ©The Mc. Graw-Hill Companies, Inc. , 2000 4 © Adapted for use at JMU by Mohamed Aboutabl, 2003

We can compare the task of network management to the task of writing a program. 1. Both tasks need rules. In network management this is handled by SMI. 2. Both tasks need variable declarations. In network management this is handled by MIB. 3. Both tasks have actions performed by statements. In network management this is handled by SNMP. 5 ©The Mc. Graw-Hill Companies, Inc. , 2000 5 © Adapted for use at JMU by Mohamed Aboutabl, 2003

23. 3 SMI 6 ©The Mc. Graw-Hill Companies, Inc. , 2000 6 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Object Identifiers All objects managed by SNMP are given an object identifier. The object identifier always starts with 1. 3. 6. 1. 2. 1. 7 ©The Mc. Graw-Hill Companies, Inc. , 2000 7 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Data Types 8 ©The Mc. Graw-Hill Companies, Inc. , 2000 8 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Simple Data Types Type Size (in bytes) Description INTEGER 4 An integer -231 to 231 - 1 Integer 32 4 Same as INTEGER Unsigned 32 4 0 to 232 - 1 OCTET STRING Variable Byte-string up to 64 K Bytes long OBJECT IDENTIFIER Variable An object identifier IPAddress 4 An IP address Counter 32 4 An integer whose value can be incremented from 0 to 232 – 1 then wraps back to 0 Counter 64 8 A 64 -bit counter Gauge 32 4 Same as Counter 32 but remains at its maximum value (without wrapping) until it is reset Time. Ticks 4 A counting value that records time in 1/100 ths of a second BITS Opaque A string of bits Variable Uninterpreted string 9 ©The Mc. Graw-Hill Companies, Inc. , 2000 9 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Structured Data Types 10 ©The Mc. Graw-Hill Companies, Inc. , 2000 10 © Adapted for use at JMU by Mohamed Aboutabl, 2003

TLV Encoding Format Tag (Hex) Type INTEGER 02 IPAddress 40 OCTET STRING 04 Counter 41 OBJECT IDENTIFIER 06 Gauge 42 NULL 05 Time. Ticks 43 Sequence, sequence of 30 Opaque 44 11 ©The Mc. Graw-Hill Companies, Inc. , 2000 11 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Length Format 12 ©The Mc. Graw-Hill Companies, Inc. , 2000 12 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Example 1: The 32 -bit INTEGER 14 13 ©The Mc. Graw-Hill Companies, Inc. , 2000 13 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Example 2: OCTET STRING “HI” 14 ©The Mc. Graw-Hill Companies, Inc. , 2000 14 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Example 3: The Object. Identifier 1. 3. 6. 1 15 ©The Mc. Graw-Hill Companies, Inc. , 2000 15 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Example 4: The IPAddress 131. 21. 14. 8 16 ©The Mc. Graw-Hill Companies, Inc. , 2000 16 © Adapted for use at JMU by Mohamed Aboutabl, 2003

23. 4 Management Information Base (MIB ver. 2) n n Each agent (i. e. managed network device) has its own MIB 2, a collection of all manageable objects inside the agent. MIB 2 classifies the objects into 10 groups 17 ©The Mc. Graw-Hill Companies, Inc. , 2000 17 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Accessing MIB Variable. Example: UDP MIB 2 n n n udp. In. Datagram : 1. 3. 6. 1. 2. 1. 7. 1 The value (instance) q 1. 3. 6. 1. 2. 1. 7. 1. 0 udp. Local. Port: 1. 3. 6. 1. 2. 1. 7. 5. 1. 2 18 ©The Mc. Graw-Hill Companies, Inc. , 2000 18 © Adapted for use at JMU by Mohamed Aboutabl, 2003

udp variables and tables 19 ©The Mc. Graw-Hill Companies, Inc. , 2000 19 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Indexes for udp. Table 20 ©The Mc. Graw-Hill Companies, Inc. , 2000 20 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Lexicographic ordering 21 ©The Mc. Graw-Hill Companies, Inc. , 2000 21 © Adapted for use at JMU by Mohamed Aboutabl, 2003

23. 5 SNMP PDUs (8 PDUs) A 0 A 1 A 5 A 3 A 2 A 7 A 6 A 8 22 ©The Mc. Graw-Hill Companies, Inc. , 2000 22 © Adapted for use at JMU by Mohamed Aboutabl, 2003

SNMP PDU format 23 ©The Mc. Graw-Hill Companies, Inc. , 2000 23 © Adapted for use at JMU by Mohamed Aboutabl, 2003

23. 6 SNMP message 24 ©The Mc. Graw-Hill Companies, Inc. , 2000 24 © Adapted for use at JMU by Mohamed Aboutabl, 2003

Get. Request message 25 ©The Mc. Graw-Hill Companies, Inc. , 2000 25 © Adapted for use at JMU by Mohamed Aboutabl, 2003

23. 7 Port numbers for SNMP 26 ©The Mc. Graw-Hill Companies, Inc. , 2000 26 © Adapted for use at JMU by Mohamed Aboutabl, 2003