Background: Know: Manager, objects , OIDs , tables , MIB , GetRequest, SNMP over UDP Recognize:
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GetNextRequest[]
This slide mainly talks about “GetNextRequest” command in SNMP PDU types . “Get” is the most frequently used command in SNMP, it is because that it the basic way to get management information from the network devices. “GetNextRequest” is used to get the next value of variable in a data table. The manager uses “GetRequest” to retrieve information from agent network devices. And the agent uses “ GetResponse” to respond the “GetRequest”. “GetRequest” and “GetNextRequest”< /span> can be used together to receive an object from a data table without knowing the identities of it. In comparison, “ GetRequest” is to get a specific object, while “GetNextRequest” is to get the next object. One of the most important function of “GetNextRequest” is the traversal of table.
e.g.
Destination | NextHop | Metric |
10.0.0.99 | 89.1.1.42 | 5 |
9.1.2.3 | 99.0.0.3 | 3 |
10.0.0.51 | 89.1.1.42 | 5 |
Firstly: NMS: GetNextRequest(ipRouteDest,ipRouteNextHop,ipRouteMetric1)
SNMP agent: GetResponse((ipRouteDest.9.1.2.3="9.1.2.3"),(ipRouteNextHop.9.1.2.3="99.0.0.3"),(ipRouteMetric1.9.1.2.3=3))
Secondly: NMS: GetNextRequest(ipRouteDest.9.1.2.3,ipRouteNextHop.9.1.2.3,ipRouteMetric1.9.1.2.3)
SNMP agent: GetResponse((ipRouteDest.10.0.0.51="10.0.0.51"),(ipRouteNextHop.10.0.0.51="89.1.1.42"),(ipRouteMetric1.10.0.0.51=5))
Thirdly: NMS: GetNextRequest(ipRouteDest.10.0.0.51,ipRouteNextHop.10.0.0.51,ipRouteMetric1.10.0.0.51 )
SNMP agent: GetResponse((ipRouteDest.10.0.0.99="10.0.0.99"),(ipRouteNextHop.10.0.0.99="89.1.1.42"),(ipRouteMetric1.10.0.0.99 =5))
Last: NMS: GetNextRequest(ipRouteDest.10.0.0.99,ipRouteNextHop.10.0.0.99,ipRouteMetric1.10.0.0.99)
Because all the information has been gotten in lexicographic order(refer to slide[!@!URL must be fixed to be a link to the corresponding wiki page rather than to PDF!@! Q6]), then the response is “endOfMibView”.
The command “GetNextRequest” should has a specified OID as reference to have access successively when SNMP operates over unreliable UDP.