{
    "mode": "man",
    "parameter": "variables",
    "section": "5",
    "url": "https://www.chedong.com/phpMan.php/man/variables/5/json",
    "generated": "2026-06-14T08:03:12Z",
    "sections": {
        "NAME": {
            "content": "variables - Format of specifying variable names to SNMP tools.\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "The syntax and semantics of management information in SNMP is given by the definitions of MIB\nobjects, loaded from one or more MIB files (or \"MIB modules\").   These  definitions  are  not\nstrictly  required  for  the  SNMP protocol to operate correctly, but are typically needed by\nSNMP client applications to display information in a meaningful manner.\n\nThe MIB file also serves as a design document when developing an SNMP  agent  (or  sub-agent)\nthat provides this information, and ensures that client and server share a common understand‐\ning about what management information represents.\n\n\nOIDs\nMIB objects are specified using Object Identifiers (OIDs), which can take a number of  forms.\nNote that all of the examples in this section refer to the same MIB object.\n",
            "subsections": [
                {
                    "name": "Numeric OIDs",
                    "content": "The fundamental format of an OID is a sequence of integer values (or \"subidentifiers\"), typi‐\ncally written using dots to separate the individual subidentifiers.\n.1.3.6.1.2.1.1.1\nThis is the format that is used within the SNMP protocol itself, in the packets that are sent\nover the network.\n\nThis  form  of representing an OID does not require MIB files or MIB object definitions to be\navailable.  However it does rely on the client application and/or network administrator know‐\ning  what a given numeric OID refers to.  As such, it is not a particularly helpful represen‐\ntation to anyone just starting out with SNMP.\n\nThis format can be obtained by giving the command-line option -On to most Net-SNMP commands.\n\n"
                },
                {
                    "name": "Full OID path",
                    "content": "A similar (but somewhat more informative) format uses the same  dotted  list  representation,\nbut with the numeric subidentifiers replaced by names, taken from the relevant MIB file(s).\n.iso.org.dod.internet.mgmt.mib-2.system.sysDescr\nThis  uniquely  identifies a particular MIB object (as with the numeric OID), but the list of\nnames should hopefully give some indication as to what information  this  object  represents.\nHowever  it does rely on the relevant MIB files being available (as do all formats other than\nthe purely numeric OID).  Such OIDs also tend to be fairly long!\n\nThis format can be obtained by giving the command-line option -Of to most Net-SNMP commands.\n\nA variant of this (typically used when writing OIDs in descriptive text, rather than  running\nprograms), is to combine the name and numeric subidentifier:\n.iso(1).org(3).dod(6).internet(1).mgmt(2).mib-2(1).system(1)\n.sysDescr(1)\n\n"
                },
                {
                    "name": "Module-qualified OIDs",
                    "content": "An  alternative way to (more-or-less) uniquely specify an OID, is to give the name of the MIB\nobject, together with the MIB module where it is defined.\nSNMPv2-MIB::sysDescr\nMIB object names are unique within a given module, so as long as there are not two  MIB  mod‐\nules  with the same name (which is unusual, though not unheard of), this format specifies the\ndesired object in a reasonably compact form.  It also makes it relatively easy  to  find  the\ndefinition of the MIB object.\n\nThis  is  the  default  format  for displaying OIDs in Net-SNMP applications.  It can also be\nspecified explicitly by giving the command-line option -OS to most Net-SNMP commands.\n\n"
                },
                {
                    "name": "Object name",
                    "content": "Possibly the most common form for specifying MIB objects is using  the  name  of  the  object\nalone - without the full path or the name of the module that defines it.\nsysDescr\nThis  is  by  far the shortest and most convenient way to refer to a MIB object.  However the\ndanger is that if two MIB modules each define a MIB object with the same name (which is  per‐\nfectly  legal in some circumstances), then it's not necessarily clear which MIB object is ac‐\ntually meant.  For day-to-day use, particularly when using  standard  MIB  objects,  this  is\nprobaby safe.  But it's important to be aware of the potential ambiguities.\n\nThis format can be obtained by giving the command-line option -Os to most Net-SNMP commands.\n\n"
                },
                {
                    "name": "UCD-format",
                    "content": "Previous versions of the code (UCD v4.x and earlier) used a simple approach to shortening the\nway OIDs were specified.  If  the  full  path  of  the  OID  began  with  .iso.org.dod.inter‐\nnet.mgmt.mib-2  then  this  prefix  was removed from the OID before displaying it.  All other\nOIDs were displayed in full.\n\nSimilarly, if an OID was passed to the UCD library that did not begin with a dot (and  wasn't\nin  the  module::name format), then the same prefix was prepended.   The example OID from the\nformats listed above would therefore be given or displayed as\nsystem.sysDescr\nThe inconsistent handling of OIDs, depending on their location within the OID tree, proved to\nbe more trouble than it was worth, and this format is no longer recommended.\n\nThe  previous behaviour can be obtained by giving the command-line option -Ou (for displaying\noutput), or -Iu (for interpreting input OIDs without a leading dot)  to  most  Net-SNMP  com‐\nmands.\n"
                }
            ]
        },
        "SEE ALSO": {
            "content": "snmpcmd(1)\n",
            "subsections": []
        },
        "BUGS": {
            "content": "The  parser of the MIB files file is not expected to handle bizarre (although correct) inter‐\npretations of the ASN.1 notation.\n\n\n\n\n\nV5.9.1                                       01 Oct 2010                                VARIABLES(5)",
            "subsections": []
        }
    },
    "summary": "variables - Format of specifying variable names to SNMP tools.",
    "flags": [],
    "examples": [],
    "see_also": [
        {
            "name": "snmpcmd",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/snmpcmd/1/json"
        }
    ]
}