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--- networking:snmp:about_snmp [2020/05/12 16:20] – [Networking - SNMP - About SNMP] peter
+++ networking:snmp:about_snmp [2020/07/15 09:30] (current) – external edit 127.0.0.1
@@ Line 23: / Line 23: @@
 ===== SNMP Manager =====
-A manager or management system is a separate entity that is responsible to communicate with the SNMP agent implemented network devices. This is typically a computer that is used to run one or more network management systems.
+A manager or management system is a separate entity that is responsible to communicate with the SNMP agent implemented network devices.
+This is typically a computer that is used to run one or more network management systems.
 SNMP Manager’s key functions
@@ Line 42: / Line 45: @@
 ===== SNMP Agent =====
-The agent is a program that is packaged within the network element. Enabling the agent allows it to collect the management information database from the device locally and makes it available to the SNMP manager, when it is queried for. These agents could be standard (e.g. Net-SNMP) or specific to a vendor (e.g. HP insight agent)
+The agent is a program that is packaged within the network element.
+Enabling the agent allows it to collect the management information database from the device locally and makes it available to the SNMP manager, when it is queried for.
+These agents could be standard (e.g. Net-SNMP) or specific to a vendor (e.g. HP insight agent)
 SNMP agent’s key functions:
@@ Line 50: / Line 57: @@
   * Signals an event to the manager.
   * Acts as a proxy for some non–SNMP manageable network node.
+{{:networking:snmp:snmp_-_agent.png?600|}}
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@@ Line 55: / Line 64: @@
 ===== Management Information database or Management Information Base (MIB) =====
-Every SNMP agent maintains an information database describing the managed device parameters. The SNMP manager uses this database to request the agent for specific information and further translates the information as needed for the Network Management System (NMS). This commonly shared database between the Agent and the Manager is called Management Information Base (MIB).
+Every SNMP agent maintains an information database describing the managed device parameters.
-Typically these MIB contains standard set of statistical and control values defined for hardware nodes on a network. SNMP also allows the extension of these standard values with values specific to a particular agent through the use of private MIBs.
+The SNMP manager uses this database to request the agent for specific information and further translates the information as needed for the Network Management System (NMS).
-In short, MIB files are the set of questions that a SNMP Manager can ask the agent. Agent collects these data locally and stores it, as defined in the MIB. So, the SNMP Manager should be aware of these standard and private questions for every type of agent.
+This commonly shared database between the Agent and the Manager is called Management Information Base (MIB).
+Typically these MIB contains standard set of statistical and control values defined for hardware nodes on a network.
+SNMP also allows the extension of these standard values with values specific to a particular agent through the use of private MIBs.
+In short, MIB files are the set of questions that a SNMP Manager can ask the agent.
+Agent collects these data locally and stores it, as defined in the MIB.
+So, the SNMP Manager should be aware of these standard and private questions for every type of agent.
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@@ Line 77: / Line 96: @@
 Every Object ID is organized hierarchically in MIB. The MIB hierarchy can be represented in a tree structure with individual variable identifier.
-A typical object ID will be a dotted list of integers. For example, the OID in RFC1213 for "sysDescr" is .1.3.6.1.2.1.1.1
+A typical object ID will be a dotted list of integers. For example, the OID in [[https://tools.ietf.org/html/rfc1213|RFC 1213]] for "sysDescr" is .1.3.6.1.2.1.1.1
+{{:networking:snmp:mib_tree.jpeg?600|}}
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@@ Line 85: / Line 106: @@
 The simplicity in information exchange has made the SNMP as widely accepted protocol. The main reason being concise set of commands, here are they listed below:
-  * GET: The GET operation is a request sent by the manager to the managed device. It is performed to retrieve one or more values from the managed device.
+  * **GET**: The GET operation is a request sent by the manager to the managed device. It is performed to retrieve one or more values from the managed device.
-  * GET NEXT: This operation is similar to the GET. The significant difference is that the GET NEXT operation retrieves the value of the next OID in the MIB tree.
+  * **GET NEXT**: This operation is similar to the GET. The significant difference is that the GET NEXT operation retrieves the value of the next OID in the MIB tree.
-  * GET BULK: The GETBULK operation is used to retrieve voluminous data from large MIB table.
+  * **GET BULK**: The GETBULK operation is used to retrieve voluminous data from large MIB table.
-  * SET: This operation is used by the managers to modify or assign the value of the Managed device.
+  * **SET**: This operation is used by the managers to modify or assign the value of the Managed device.
-  * TRAPS: Unlike the above commands which are initiated from the SNMP Manager, TRAPS are initiated by the Agents. It is a signal to the SNMP Manager by the Agent on the occurrence of an event.
+  * **TRAPS**: Unlike the above commands which are initiated from the SNMP Manager, TRAPS are initiated by the Agents. It is a signal to the SNMP Manager by the Agent on the occurrence of an event.
-  * INFORM: This command is similar to the TRAP initiated by the Agent, additionally INFORM includes confirmation from the SNMP manager on receiving the message.
+  * **INFORM**: This command is similar to the TRAP initiated by the Agent, additionally INFORM includes confirmation from the SNMP manager on receiving the message.
-  * RESPONSE: It is the command used to carry back the value(s) or signal of actions directed by the SNMP Manager.
+  * **RESPONSE**: It is the command used to carry back the value(s) or signal of actions directed by the SNMP Manager.
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@@ Line 97: / Line 118: @@
 ===== Typical SNMP communication =====
-Being the part of TCP⁄ IP protocol suite, the SNMP messages are wrapped as User Datagram Protocol (UDP) and intern wrapped and transmitted in the Internet Protocol. The following diagram will illustrate the four–layer model developed by Department of Defense (DoD).
+Being the part of TCP⁄ IP protocol suite, the SNMP messages are wrapped as User Datagram Protocol (UDP) and intern wrapped and transmitted in the Internet Protocol.
+The following diagram will illustrate the four–layer model developed by Department of Defense (DoD).
+{{:networking:snmp:snmp_-_layers.png?600|}}
+__GET⁄ GET NEXT⁄ GET BULK⁄ SET__
+{{:networking:snmp:snmp_-_get_-_response.gif?600|}}
+__TRAP__
+{{:networking:snmp:snmp_-_trap.gif?600|}}
+__INFORM__
+{{:networking:snmp:snmp_-_inform_-_acknowledgment.gif?600|}}
 By default SNMP uses port 161 and TRAP⁄ INFORM uses port 162 for communication.
@@ Line 109: / Line 146: @@
 ==== SNMPv1: ====
-This is the first version of the protocol, which is defined in RFCs 1155 and 1157
+This is the first version of the protocol, which is defined in [[https://tools.ietf.org/html/rfc1155|RFC 1155]] and [[https://tools.ietf.org/html/rfc1157|RFC 1157]].
 ==== SNMPv2c: ====
-This is the revised protocol, which includes enhancements of SNMPv1 in the areas of protocol packet types, transport mappings, MIB structure elements but using the existing SNMPv1 administration structure ("community based" and hence SNMPv2c). It is defined in RFC 1901, RFC 1905, RFC 1906, RFC 2578.
+This is the revised protocol, which includes enhancements of SNMPv1 in the areas of protocol packet types, transport mappings, MIB structure elements but using the existing SNMPv1 administration structure ("community based" and hence SNMPv2c). It is defined in [[https://www.ietf.org/rfc/rfc1901.txt|RFC 1901]], [[https://tools.ietf.org/html/rfc1905|RFC 1905]], [[https://tools.ietf.org/html/rfc1906|RFC 1906]], [[https://tools.ietf.org/html/rfc2578|RFC 2578]].
 ==== SNMPv3: ====
-SNMPv3 defines the secure version of the SNMP. SNMPv3 also facilitates remote configuration of the SNMP entities. It is defined by RFC 1905, RFC 1906, RFC 3411, RFC 3412, RFC 3414, RFC 3415.
+SNMPv3 defines the secure version of the SNMP. SNMPv3 also facilitates remote configuration of the SNMP entities. It is defined by [[https://tools.ietf.org/html/rfc1905|RFC 1905]], [[https://tools.ietf.org/html/rfc1906|RFC 1906]], [[https://tools.ietf.org/html/rfc3411|RFC 3411]], [[https://tools.ietf.org/html/rfc3412|RFC 3412]], [[https://tools.ietf.org/html/rfc3414|RFC 3414]], [[https://tools.ietf.org/html/rfc3415|RFC 3415]].
 Though each version had matured towards rich functionalities, additional emphasis was given to the security aspect on each upgrade. Here is a small clip on each editions security aspect.