12.1 SNMP MIBs

12.1 SNMP MIBs The Simple Network Management Protocol (SNMP) provides a means to help manage networks. SNMP is essentially the only network management protocol in use today. SNMP uses Management Information Bases (MIBs) to establish a consistent language between all SNMP-speaking devices. A MIB is written in human-readable MIB language and is saved as a text file. Network management administrators must compile the MIBs that interest them into the proprietary binary format of their network management software. Once this is done, users can browse the MIBs using the network management software. Public MIBs exist as RFCs. A MIB RFC provides a brief description of the intended use of the MIB and includes the contents of the MIB. If you need to compile a MIB in your network management software, you can copy and paste the RFC text, being careful to delete each page's header and footer. You can usually find versions of public MIBs on Web sites in a ready-to-compile form. One such site is http://www.aciri.org/fenner/mibs/mib-index.html. Router vendors support a subset of the public MIBs available, depending on the protocols that run on their routers. Check your router vendor's technical documentation to determine the MIBs it supports. Juniper Networks lists the public MIBs it supports in its Installation and System Management guide. In addition to public MIBs, many vendors provide proprietary MIBs for information specific to their products. Juniper Networks' proprietary MIBs are available at http://www.juniper.net/techpubs/mibs.html. An SNMP daemon runs on each router, and SNMP software runs on one or more network management systems (NMS). SNMP MIBs contain two types of entities, namely traps and objects. SNMP traps are pushed from the router to the NMS, without the NMS requesting the information. SNMP traps are sent when a specific event occurs (for example, a link or adjacency in the networks goes down). MIB objects can be polled from the NMS. They can either be polled manually�a practice known as MIB browsing�or they can be polled periodically and used for graphs of historical data. You can find free NMS software on the Web. The authors' favorite is Active SNMP, which is available at http://www.cscare.com/ActiveSNMP/. When an NMS sends an SNMP request to a router, it identifies the MIB object in which it is interested by the object identifier (OID). OIDs are hierarchical, with each level separated by a dot in the standard notation. Each named level of hierarchy is assigned a number. The following lists where various MIBs are rooted: Public MIBs: .iso.org.dod.internet.mgmt.mib-2 = .1.3.6.1.2.1 Proprietary MIBs: .iso.org.dod.internet.private.enterprises = .1.3.6.1.4.1 Experimental MIBs: .iso.org.dod.internet.experimental = .1.3.6.1.3 To know where a MIB fits into the hierarchy, read the MODULE-IDENTITY section of the MIB. For example the MODULE-IDENTITY of the ipMRouteStdMIB MIB is the following: ipMRouteStdMIB MODULE-IDENTITY LAST-UPDATED "200009220000Z" -- September 22, 2000 ORGANIZATION "IETF IDMR Working Group" CONTACT-INFO " Dave Thaler Microsoft Corporation One Microsoft Way Redmond, WA 98052-6399 US Phone: +1 425 703 8835 EMail: dthaler@microsoft.com" DESCRIPTION "The MIB module for management of IP Multicast routing, but independent of the specific multicast routing protocol in use." REVISION "200009220000Z" -- September 22, 2000 DESCRIPTION "Initial version, published as RFC 2932." ::= { mib-2 83 } The last line of the preceding output shows that this MIB fits into the MIB-2 hierarchy with OID 83. The following shows the full OID of the ipMRouteStdMIB (both named and numeric representation): .iso.org.dod.internet.mgmt.mib-2.ipMRouteStdMIB = .1.3.6.1.2.1.83 12.1.1 Multicast Routing MIB (ipMRouteStdMIB) The IPv4 multicast routing MIB (ipMRouteStdMIB) is defined in RFC 2932. The MIB contains objects that are not specific to any protocol and are needed to manage a multicast network. The MIB contains the following tables: IP Multicast Route Table: Multicast route information including RPF neighbor and the name of the multicast routing protocol being used IP Multicast Routing Next-Hop Table: Information on the downstream interface list for particular source-group pairs IP Multicast Routing Interface Table: Interface information specific to multicast routing IP Multicast Scope Boundary Table: Boundary interfaces configured for administratively scoped multicast IP Multicast Scope Name Table: Names of the multicast scopes configured on the router 12.1.2 IGMP MIB (igmpStdMIB) The IGMP MIB is defined in RFC 2933. It contains information about IGMP-enabled interfaces and current group membership of directly attached hosts. The OID is as follows: .iso.org.dod.internet.mgmt.mib-2.igmpStdMIB = .1.3.6.1.2.1.85 The MIB contains the following two tables: IGMP Interface Table: Information about interfaces configured for IGMP IGMP Cache Table: Information about hosts that have joined multicast groups using IGMP 12.1.3 PIM MIB (pimMIB) The PIM MIB is specified in RFC 2934. The PIM MIB contains information about PIM interfaces, neighbors, RP group mappings, and multicast routing tables. The OID is as follows: .iso.org.dod.internet.experimental.pimMIB = .1.3.6.1.3.61 The MIB contains the following tables: PIM Interface Table: Information about each of the router's PIM interfaces PIM Neighbor Table: Information about each of the router's PIM neighbors PIM IP Multicast Route Table: Information on PIM Join state from the perspective of the upstream interface PIM Next-Hop Table: Information on PIM Join state from the perspective of the downstream interface list PIM RP Table (deprecated): PIMv1 RP information PIM RP-Set Table: BSR RP-set information PIM Candidate RP Table: BSR candidate RP information PIM Component Table: Information on each of the PIM domains to which the router is connected 12.1.4 MSDP MIB (msdpMIB) The MSDP MIB is specified in an IETF draft maintained by the MSDP working group. The MIB contains information on MSDP peers and the Source-Active cache. The OID is as follows: .iso.org.dod.internet.experimental.msdpMIB = .1.3.6.1.3.92 The MSDP MIB contains the following tables: Requests Table: The longest-match table used to determine the peer to which SA Requests are sent for a given group Peer Table: Information on each of the router's MSDP peers Source-Active Cache Table: Information about the SA cache