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THIS DOCUMENT PROVIDES INFORMATION WITH RESPECT TO DIFFERENT SNMP MESSAGES AND WHAT ALL SNMP MESSAGES DOES VEGA SUPPORTS
SNMP Messages
Table as given below shows the list of SNMP Messages and whether they are supported in VEGA or not.
Sl. No. | SNMP Message | VEGA Support |
1 | SNMP Trap | Y |
2 | SNMP Get | Y |
3 | SNMP Set | Y |
4 | SNMP GetNext | Y |
5 | SNMP GetBulk | Y |
6 | SNMP Walk | Y |
7 | SNMP InformRequest | N |
8 | SNMP Response | Y |
Please find the description and example with respect to all SNMP messages as supported by VEGA:
SNMP Trap
This message is initiated by an SNMP Agent and sent to the SNMP Manager. For example, the VEGA (SNMP Agent) could send a message to the SNMP Manager that VEGA has went down and restarted.
This is termed an SNMP Trap. Basically, it is an alarm telling the Manager that the VEGA has been restarted.
It can also be used by network entities to signal abnormal conditions to management stations. A "cold-trap" is sent when device hard reboots, and in case device performs a software reload a "warm-trap" is sent to the manager on start-up.
Below pcap trace image shows the SNMP TRAP triggered by VEGA when VEGA box comes up after reboot (COLD START):
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SNMP Get
This message is initiated by the SNMP Manager when it wants to retrieve some data from an SNMP Agent. SNMP GET is a request to query for information on a network entity. One or more object identifiers (OIDs) may be given as arguments on the command line in case of using snmpget application or Manager may send more than one OID's in its SNMP GETrequest.
For example as given below:
SNMP Get Command |
SNMP Get For SNMPv1 snmpget -v1 -c public 192.168.3.199 1.3.6.1.2.1.1.6 SNMP Get For SNMPv2c snmpget -v2c -c public 192.168.3.199 1.3.6.1.2.1.1.6 SNMP Get For SNMPv3 snmpget -v3 -u public -c public 192.168.3.199 1.3.6.1.2.1.1.6 |
Below pcap trace image shows the SNMP GET Request received at vega and VEGA sending response for the same.
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SNMP SET
(As of now only supported for sysLocation and sysContact) This message is initiated by the SNMP Manager that is sent when the operator wants to change data on a network element i.e. modify information on the remote host
For example as given below:
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| Info |
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Important NOTE Only Contact and Location Variables are set permanently on VEGA using set command and will not get reset even if the device is rebooted. |
SNMP GetNext
This message is initiated by the SNMP Manager when it wants to retrieve some data from an SNMP Agent of the next variable for which request has been sent. Returns a Response with variable binding for the next variable in the MIB. The entire MIB of an agent can be walked by iterative application of GetNextRequest starting at OID 0. Rows of a table can be read by specifying column OIDs in the variable bindings of the request.
It is mainly request to query a network entity efficiently for information, , is used to retrieve the next oid in the mib tree of data.
For example as given below:
SNMP GetNext Command for SNMPv2c
snmpgetnext -m all -v2c -c public 192.168.3.199 1.3.6.1.2.1.2.2.1.1
Below pcap trace image shows the SNMP GETNEXT Request received at vega and VEGA sending response for the same.
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SNMP GetBulk
This message is initiated by the SNMP Manager when it wants to retrieve data from SNMP Agent. This is basically a multiple iteration of GetNext Request untill t reached to the maximum limit which SNMP Agent can sent in a single SNMP Response. Returns a Response with multiple variable bindings walked from the variable binding or bindings in the request. PDU specific non-repeaters and max-repetitions fields are used to control response behavior and is introduced in SNMPv2. Max-repetitions mainly shows number of variable binding does the SNMP GetBulk request needs to retrieve from VEGA.
For example as given below where snmpbulkget application is used to get response from SNMP Agent i.e. VEGA:
SNMP Bulk Get Command for SNMPv2c
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Below pcap trace image shows the SNMP BULKGET Request received at vega and VEGA sending response for the same.
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SNMP Walk
snmpwalk is an SNMP application that uses SNMP GETNEXT requests to query a network entity for a tree of information. An object identifier (OID) may be given on the command line.This OID specifies which portion of the object identifier space will be searched using GETNEXT requests
For example as given below where snmpwalk application is used to get response from SNMP Agent i.e. VEGA:
SNMPWALK Command For SNMPv2c
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NOTE SNMP Inform Request is not supported in VEGA In all above SNMP message examples:
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SNMP Message Format
Each SNMP message contains the following:
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