Cisco SRST User Guide - Page 44

Internet MIB Hierarchy Chapter 1 Cisco SRST SNMP MIB Support As shown in Figure 1-3, the SNMP agent gathers data from the MIB, which is the repository for information about device parameters and network data. The agent can send traps, or notifications of events of interest, to the manager. The Cisco trap file, mib.traps, which documents the format of the Cisco traps, is available on the Cisco host ftp.cisco.com. Figure 1-3 Simple Network Management Protocol Network The SNMP manager uses information in the MIB to perform the operations described in Table 1-5. Table 1-5 SNMP Manager Operations Operation get-request get-next-request get-response get-bulk-request set-request trap Description Retrieve a value from a specific variable. Retrieve the value following the named variable. Often used to retrieve variables from within a table. 1 The reply to a get-request, get-next-request, get-bulk-request, or set-request sent by an NMS. Similar to a get-next-request, but fill the get-response with up to max-repetition number of get-next interactions. Store a value in a specific variable. An unsolicited message sent by an SNMP agent to an SNMP manager indicating that some event has occurred. 1. With this operation, an SNMP manager does not need to know the exact variable name. A sequential search is performed to find the needed variable from within the MIB. Internet MIB Hierarchy The MIB structure is logically represented by a tree hierarchy (see Figure 1-4). The structure uses branches and the branches that fall below each category have short text strings and integers to identify them. Text strings describe object names, and integers allow computer software to create compact, encoded representations of the names. For example, the Cisco MIB variable authAddr is an object name and is denoted by number 5, which is listed at the end of its object identifier number 1.3.6.1.4.1.9.2.1.5. The object identifier in the Internet MIB hierarchy is the sequence of numeric labels on the nodes along a path from the root to the object. The Internet standard MIB is represented by the object identifier 1.3.6.1.2.1. It also can be expressed as iso.org.dod.internet.mgmt.mib. (See Figure 1-4.) 1-30 Cisco SRST SNMP MIB Release 3.4 Guide OL-7959-01