Transcript Adding Remote Management with SNMP

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SNMP
Simple Network Management Protocol
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Why was SNMP invented ?
Designed to run on non-OS systems, later used in various ways for monitoring
Maybe no (Free) Cpu
 Maybe no (Free)
Memory
 Must be able to run
everywhere
No “BRAINS”
SNMP Agent

THE “BRAINS”
SNMP Manager
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Real OS
 Contained all intelligence
 Made all decisions

Protocol, its versions and extentions
What is SNMP
About the protocol versions
SNMPv1,
SNMPv2 ( c ) and SNMPv3
Some other things:
RMON, RMON 2, SMI's and MIB's
SNMPv3 - as a future path for SNMP
community ?
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SNMP implementations
 Transport


Transport protocol (UDP/IP)
BER (iso 8825) - Basic Encoding Rules

TLV (Type, Length, Value) encoding
 Versions



SNMPv1
SNMPv2
SNMPv3
 OSI

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network management implementation
CMIP - CMOT ( used primarily in telephony along with
SNMP)
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SNMP Syntax - SMI
ASN.1 (iso 8824 - “abstract notation one”)
 SMI uses a subset of ASN.1
 Well
defined syntax for information exchange
 comparable
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in functionality with XML
SNMPv3
 New
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Draft Standard with enhanced Security

User Based security model (rfc 2574)

Administration

Security (authentication, privacy and message integrity)

View based access (VACM)
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RMON (Remote Network Monitoring)
 IETF rfc
1271 / rfc 1757 / rfc 1513
 Physical Layer Management using probes (HW-SW)
 Extend SNMP functionality

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RMON MIB : contains RMON data
Preventive Management : threshold based notification
Statistics/History of data, Packet capturing, Host tables,…
Operation modes



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Online
Offline
On Demand
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RMON2
 Continued
on RMON (rfc 2021)
 Statistics on network and upper layers
 All of the leading probe vendors support it

NetScout, Technically Elite, Solcom, HP, 3Com, Bay, Cisco,
Cabletron
 Difficult
to use all features because of vendor specific
implementations
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SNMP References
SNMP v1 RFCs
 1155
SMI
 1157
protocol
 1212
Concise MIB
 1213
MIB2
 1215
traps
SNMP v2 RFCs
 historical
See also : The Simple Web
http://snmp.cs.utwente.nl/
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SNMP v2C RFCs
 1902-1907
SNMP v3 RFCs
 1905-1907
 2571-2575
 2578-2580
http://www.ietf.org
UDP vs. TCP connection
UDP • connectionless
• scalable
• not reliable
TCP • connection oriented
• used to be non-scalable
• reliable
Agents
Agents
RM
Console
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Console
SNMP : Underlying Transport
UDP/IP implications
unreliable
 no confirmation or guarantee
 order uncertain
 may duplicate
unsecure
 No authentication on transport layer
 No verification of origin (message spoofing)
 No integrity (message can be tampered with)
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The SNMP Agent
What is an SNMP agent ?
 Components :
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
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MIB (the MIB in memory)
request handling
trap sending
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Multiple SNMP Agents on 1 system
Conflict : only 1 process can listen on a port
Solutions :
 SMUX (SNMP Multiplexer)
 AgentX - Agent Extensibility (rfc 2741)
 Emanate (proprietary SNMP Research)
Sub agent
Master
Agent
Sub agent
Application
Application
161
Sub agent
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Device
MIB (Management Information Base)
 The


textual description of MIB layout
Written in SMI : Structure of Management Information
 SMI


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MIB definition
(the MIB definition language)
Support for multiple datatypes
Support for data definitions : indexed tables, structures,
values,...
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NAMING in SNMP
iso
1
Naming hierarchy
unique identifier, down to the 3 org
instance of any object
6 dod
1.3.6.1.4.1.1031 is the OID of
1 internet
the BMC Software subtree;
2
4 private
mgmt
Object identifier is
1 enterprises
the name
enterpriseID
442
peer 1031
BMC
Company X
Whatever you like
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SNMP Management
Remote Management :
From a geographically
separate location
 configure
 monitor
 control
a remote system
 application
 device
 OS
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Management console
Mgmt protocol
Mgmt info,
i.e.,
interesting
info
“application”
Managed system
Management Operations,
SNMP requests and responses
 Get,


Get Next, Set
SNMPv1
responses are sent back
 Get
Bulk (SNMPv2)
 Unsolicited
 Informs
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Traps from Agent (v1)
(v2 and v3) - confirmed traps
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Request handling
 SNMP Agent


gets request from mgr
listens on specific port : typically 161
receives request : request ID + OID
 Lookup
of OID in memory
 Performs operation if possible
 SNMP Agent sends response




request ID
OID
value
error status + index
 Similar
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for get-next operation
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
returns next OID in tree
Trap sending
SNMP Agent sends
 7 predefined Generic trap types (0-6)

0-5 = Standard traps

6 = Enterprise Specific
 Sends
to port 162 (default) on trap receiving
machine
 Trap

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destinations has to be configured
Patrol : /snmp/piV1m_list
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The SNMP Manager
What is an SNMP manager ?
Components :
 present MIB info (display MIB files)
 send requests
 listen for traps
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Sending Requests
 Timebased
polling
 User based requests
Authentication :
 SNMPv1 : community names for r/w (most of the
times, just private/public)
 SNMPv3 does it with MD5
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