CSEE W4140
Networking Laboratory
Lecture 11: SNMP
Jong Yul Kim
04.15.2009
Annoucements
 Visit to
TelioSonera’s NY
POP
Wed
Fri
1
Gowri
Philip
2
Jia
Gaurav
3
Tian
Jordan
4
Ramachandran
Da Quan
5
Defeng
Cesar
6
Ankit
7
Jorge
8
Hai
9
Guangyao
10
Apar
11
Aaron
12
Siming
13
Eric
14
Aniruddha
15
Suhas
16
Justin
17
Adam
18
Palak
19
Adnan
Network management
 Network operators need tools to monitor and manage
networks remotely.
 True even if the network is relatively small.
 Examples:
 How many IP fragments did this router create?
 How long has the server been running?
 Which host is about to shutdown?
 Types of management
 Performance
 Fault
Network management architecture
Components of the network
management architecture

Managing entity is the central management station within the network:
“the administrator’s console”

Managed device is the machine we’re interested in monitoring /
controlling

Managed objects are pieces of hardware within the managed device, e.g.
network interface card, and the set of configurations for hardward and
software

Management Information Base (MIB) is the information of interest
related to managed objects, e.g. routing table

Network management agent is a program that runs on the managed
device which communicates with the managing entity.

Network management protocol is the protocol used between the agent
and the managing entity
Four parts of SNMP
1. Network management objects
 Management Information Base (MIB)
 This is the value that we’re interested in
monitoring or controlling.
 A MIB module is a collection of related MIBs.
2. Data definition language
 Structure of Management Information (SMI)
 This defines the format of MIBs such as data
type and object model.
Four parts of SNMP
3. Protocol


Simple Network Management Protocol (SNMP)
This is the protocol used between the managing
entity and the agent.
4. Security and administration capabilities
 MIB and SMI are independent of the
protocol. The protocol is independent of
MIB and SMI.
SMI
 SMI is used to define the syntax and
semantics of management objects.
 It defines basic data types and higher level
constructs, such as OBJECT-TYPE and
MODULE-TYPE.
 SMI is a subset of ASN.1 (Abstract Syntax
Notation 1), which adopts a
{machine,OS,language}-independent
method for describing data and rules for
transmitting that data
SMI basic data types
SMI OBJECT-TYPE
ipForwDatagrams OBJECT-TYPE
SYNTAX Counter
ACCESS read-only
STATUS current
DESCRIPTION
"The number of input datagrams for which this
entity was not their final IP destination, as a
result of which an attempt was made to find a
route to forward them to that final destination.
In entities which do not act as IP Gateways, this
counter will include only those packets which were
Source-Routed via this entity, and the SourceRoute option processing was successful."
::= { ip 6 }
Object Identifier (OID)
MIB module
Organization of managed
objects

.
Organized in a tree-like
hierarchy
root
iso(1)

Each node is named with
an OID.

OIDs reflect the structure
of the hierarchy.
org (3)
dod (6)
internet (1)


The OID 1.3.6.1.2.1
(iso.org.dod.internet.mgm
t.mib-2) is at the top of
the hierarchy for all
managed objects of the
MIB-II.
directory (1)
experimental (3)
private (4)
mib-2 (1)
system (1)
Manufacturers of
networking equipment can
add product specific
objects to the hierarchy.
mgmt (2)
at (3)
interface (2)
icmp (5)
ip (4)
ipForwDatagrams (6)
tcp (6)
udp (7)
egp (8)
snmp (11)
transmission (10)
MIBs
 A MIB specifies the managed objects, which have
OIDs.
 The OID is specified in a MIB file.
 In Linux, MIB files are in the directory
/usr/share/snmp/mibs
 Multiple MIB files
 MIB-II (defined in RFC 1213) defines the managed
objects of TCP/IP networks
 When an SNMP manager requests an object, it sends
the OID to the SNMP agent.
UDP Example
SNMP Protocol
 SNMP manager and an SNMP agent
communicate using the SNMP protocol
 Generally: Manager sends queries and agent
responds
 Exception: Traps are initiated by agent.
Notice UDP port 161
SNMP message types
Traps
 Traps are messages that are asynchronously sent by
an agent to a manager
 Traps are triggered by an event
 Defined traps include:
 linkDown: Even that an interface went down
 coldStart - unexpected restart (i.e., system crash)
 warmStart - soft reboot
 linkUp - the opposite of linkDown
 (SNMP) AuthenticationFailure
Homework
 Prelab 9 due this Friday
 Please write your own answers!
 Lab report 8 due next week before
labs
Main Points of Lab 9
 SNMP




MIBs
SNMP requests and responses
Security
Traps
 Note: You need to download files
from web and bring it to the lab
http://www.comm.utoronto.ca/~jorg/teaching/itlab/links/conf/lab9/snmpd.conf