Exploring the Net-SNMP MIB

Aims

  • To develop understanding of the structure of a MIB
  • To discover details of the types of information contained in a MIB
  • To learn how to use SNMP as a source of network and host management information

Resources

Exercises

  1. Verify that your SNMP utility software is installed and operational. If not, then see previous exercises and install it.
    For example, try the command:
    snmpwalk -v2c -c netLAB netlabGW.netlab system
    or if you are outside the NetLAB:
    snmpwalk -v1 -c MRTGview waserv.netcomp.monash.edu.au system

  2. Recall that the SNMP version 2 Management Information Base (MIB) is structured as shown in the diagram below:

    T08SNMPMIB.jpg
  3. Complete the following table of MIB object descriptions:

    MIB category ISO numeric Object ID contains information about... 
    system
    .1.3.6.1.2.1.1


    interfaces
    .1.3.6.1.2.1.2

    arp
    .1.3.6.1.2.1.3

    ip
    .1.3.6.1.2.1.4

    icmp
    .1.3.6.1.2.1.5

    tcp
    .1.3.6.1.2.1.6

    udp
    .1.3.6.1.2.1.7


  4. Enter the ISO numeric Object ID value and MIB category name for the following MIB objects?

    MIB Object ID ISO numeric Object ID MIB Category?        Current Value...................
    sysUpTime.0
    .1.3.6.1.2.1.1.3.0 system
    30869111 Timeticks = 3 days, 13:44:51.11
    ifNumber.0



    ifMtu.1 or .2



    ipDefaultTTL.0



    ipInReceives.0



    ipForwDatagrams.0



    ipOutNoRoutes.0



    ipReasmOKs.0



    ipFragOKs.0



    icmpInEchos.0



    tcpRtoMin.0



    tcpMaxConn.0



    tcpInSegs.0



    udpInDatagrams.0



    egpInMsgs.1


    "...no such object..."

  5. Use a utility program such as snmpget or snmpwalk to display the current values of the MIB Objects identified in the table above.

  6. An application requires that you produce some statistics about your network. List the SNMP MIB OID's that you could used as source values to calculate the following statistics, and show the arithmetic that would be needed in each case:

    Statistic
    Source OIDs......................
    Arithmetic formulae..........................
    packets per second
    (assume 5 minute sample intervals
    and dont forget to convert
    from Timeticks into Seconds !!
    )





    Kbyte per second
    (assume 5 minute sample intervals
     and that K = 210 = 1024
    )





    Average % channel utilisation
    (assume 5 minute sample intervals)






    Average % error rate
    (errors include runts,
    dropped packets and checksum errors
    )






  7. Devise a way to traverse the entire MIB tree and inspect all objects found.
    Is there a better way to find out what information may be found in a MIB?
    (Hint: does the system MIB contain metadata about the MIB?)