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Unformatted text preview: ing of the object identifiers, not
the human-readable names.
2. The ordering of the rows in a table depends on the values of the indexes for the table. In
Figure 25.13, 67 is lexicographically less than 161, which is lexicographically less than 520.
Figure 25.14 shows this column-row order for our sample UDP listener table. file:///D|/Documents%20and%20Settings/bigini/Doc...omenet2run/tcpip/tcp-ip-illustrated/snmp_sim.htm (10 of 33) [12/09/2001 14.47.40] Chapter 25. SNMP: Simple Network Management Protocol Figure 25.14 UDP listener table, showing column-row ordering.
We'll also see this column-row ordering when we use the get-next operator in the next section. 25.7 Simple Examples
In this section we'll show some examples that fetch the values of variables from an SNMP agent.
The software used to query the agent is called snmpi and is from the ISODE system. Both are
described briefly in [Rose 1994].
We'll query a router for two simple variables from the UDP group:
sun % snmpi -a gateway -c secret
snmpi> get udpInDatagrams.0 udpNoPorta.0
The -a option identifies the agent we want to communicate with, and the -c option specifies the
SNMP community. It is a password supplied by the client (snmpi in this case) and if the server (the
agent in the system gateway) recognizes the community name, it honors the manager's request.
An agent could allow clients within one community read-only access to its variables, and clients in
another community read-write access.
The program outputs its snmpi> prompt, and we can type commands such as get, which
translates into an SNMP get-request message. When we're done, we type quit. (In all further
examples we'll remove this final quit command.) Figure 25.15 shows the two lines of tcpdump
output for this example.
1 0.0 2 0.348875
(0.3489) sun.1024 > gateway.161: GetRequest(42)
gateway.161 > sun.1024: GetResponse(46)
Figure 25.15 tcpdump output for simple SNMP query. The request for the two varia...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.
- Spring '12