OSPF Version 2 Management Information Base
obsoletes
- rfc-1850 — OSPF Version 2 Management Information Base
Extracted elements (27)
Interface metrics are placed in a separate ospfIfMetricTable rather than inline in ospfIfTable to simplify dealing with multiple types of service (TOS). This separation allows multiple metric rows per interface without complicating the primary interface table structure.
SNMPv3 Contexts are recommended for managing multiple OSPF instances on the same system, providing MIB views per instance without requiring separate MIB structures. This leverages existing SNMPv3 infrastructure rather than embedding instance indexes throughout the MIB.
The LSDB table (ospfLsdbTable) is provided primarily for network debugging rather than for operational management. The raw ospfLsdbAdvertisement OCTET STRING exposes the full LSA contents but SNMP agents may not be able to return the largest variable-length LSAs due to SNMP message size constraints.
The ospfAreaRangeTable (OID ospf 5) is marked obsolete and replaced by the ospfAreaAggregateTable, which provides a more capable address range summarization mechanism. The obsolete table is retained for backwards compatibility with RFC 1850 implementations.
The ospfDiscontinuityTime object records the sysUpTime of the most recent counter discontinuity event. This is needed because Counter32 objects wrap and can be reset by process restarts; without a discontinuity timestamp, management stations cannot distinguish a counter reset from normal operation.
Trap throttling guidance in Section 4 recommends that implementations suppress excessive traps (e.g., from flapping interfaces) and optionally ignore initial activity at startup. The MIB separates the trap definitions into their own optional module to allow deployments that do not require trap support to omit it entirely.
ospfRFC1583Compatibility controls external path preference behavior. When enabled, only cost is used to choose among multiple AS-external LSAs for the same destination (RFC 1583 behavior). When disabled, path type preference (intra-area > inter-area > external) takes precedence, with cost only as a tiebreaker (RFC 2328 behavior). Mixing modes in an AS can cause routing loops.
RFC 4750 obsoletes RFC 1850 but is designed to be backwards compatible. Changes include new objects for NSSA, Opaque LSA, graceful restart, stub router, reference bandwidth, RFC1583 compatibility, and area LSA counting. The ospfAuthType per-area object is deprecated in favor of per-interface ospfIfAuthType. See Appendix B for the full change list.
Management entities reading OSPF counters (ospfOriginateNewLsas, ospfRxNewLsas, ospfSpfRuns, ospfIfEvents, ospfNbrEvents, etc.) SHOULD check ospfDiscontinuityTime to detect events (such as OSPF process restarts) that would invalidate their understanding of counter values.
Management stations SHOULD include as many columnar read-write objects as possible in a Set-Request when creating a conceptual row. Agents should accept Set-Requests with as few objects as needed, consistent with the Robustness Principle ('be liberal in what you accept, conservative in what you send', RFC 791).
ospfExtLsdbLimit MUST be set identically in all routers attached to the OSPF backbone and any regular OSPF area. Stub areas and NSSAs are excluded from this requirement. When the non-default AS-external LSA count reaches this limit, the router enters overflow state.
ospfIfHelloInterval must be the same for all routers attached to a common network; the default is 10 seconds. Similarly, ospfIfRtrDeadInterval must be the same for all routers on a common network; the default is 40 seconds (four times the Hello interval).
ospfIfTransitDelay and ospfIfRetransInterval each have a minimum value that SHOULD be 1 second. Their defaults are 1 second and 5 seconds respectively.
Persistent MIB objects (ospfRouterId, ospfAdminStat, ospfASBdrRtrStatus, ospfTOSSupport, ospfExtLsdbLimit, ospfExitOverflowInterval, ospfRFC1583Compatibility, ospfReferenceBandwidth, ospfRestartSupport, ospfRestartInterval, ospfRestartStrictLsaChecking, ospfStubRouterAdvertisement, and various interface/area table objects) SHOULD be saved to non-volatile storage when written.
Graceful restart support is represented by ospfRestartSupport (none/plannedOnly/plannedAndUnplanned), ospfRestartInterval (1–1800 seconds), ospfRestartStrictLsaChecking, ospfRestartStatus (notRestarting/plannedRestart/unplannedRestart), ospfRestartAge (remaining seconds), and ospfRestartExitReason (none/inProgress/completed/timedOut/topologyChanged).
Stub router functionality is exposed via ospfStubRouterSupport (read-only capability flag) and ospfStubRouterAdvertisement (doNotAdvertise/advertise), which controls whether the router advertises stub router LSAs as described in the OSPF Stub Router Advertisement specification.
The ospfAreaNssaTranslatorStabilityInterval (default 40 seconds) specifies how long an elected NSSA translator continues performing translation duties after determining its services are no longer required. This prevents translator flapping during election transitions.
The ospfAreaTable (OID ospf 2) describes configured parameters and statistics for each OSPF area, including area ID, authentication type, import policy (importExternal/importNoExternal/importNssa), SPF run count, ABR/ASBR counts, LSA count, NSSA translator role and state, and translator stability interval. Area 0.0.0.0 is always the backbone.
The OspfAuthenticationType textual convention defines three authentication types: none (0), simplePassword (1), and md5 (2). Values above 2 are reserved for specification by IANA. This type is used in both ospfIfAuthType (per-interface) and the deprecated ospfAuthType (per-area).
The ospfGeneralGroup (OID ospf 1) contains global variables for the OSPF process, including ospfRouterId (32-bit router identifier), ospfAdminStat (enabled/disabled), ospfVersionNumber (fixed at 2), ospfExternLsaCount, ospfOriginateNewLsas, ospfRxNewLsas, and ospfDiscontinuityTime. These apply globally across all OSPF interfaces on the device.
The ospfIfMetricTable (OID ospf 8) is an adjunct to ospfIfTable that stores per-interface, per-TOS metrics separately to simplify multi-TOS management. The default TOS-0 metric is calculated as referenceBandwidth / ifSpeed, where the default reference bandwidth is 10^8 bits/second (100 Mbps).
The ospfIfTable (OID ospf 7) describes each OSPF interface, carrying fields for IP address, area ID, interface type (broadcast/nbma/pointToPoint/pointToMultipoint), admin status, router priority, transit delay, retransmission interval, Hello interval, dead interval, poll interval, state, designated router IP and Router ID, backup DR, event counter, authentication key, authentication type, and link-local LSA statistics.
The ospfLsdbTable (OID ospf 4) represents the per-area link state database, indexed by AreaID, LSA type, Link State ID, and Router ID. Each entry exposes the LSA sequence number (signed 32-bit, starting at 0x80000001), age in seconds, Fletcher checksum, and the full raw advertisement as an OCTET STRING.
Several objects in the OSPF MIB pose significant security risks. In particular, ospfIfAuthType and ospfIfAuthKey can be used to engage in significant attacks against an OSPF router by altering authentication configuration. The use of SNMPv3 with authentication and privacy is strongly recommended for management access.
The use of simplePassword authentication (ospfIfAuthType = simplePassword) is explicitly NOT recommended when there is concern about attacks on the OSPF system. Simple password authentication re-uses cleartext passwords per RFC 1704 and is only sufficient to protect against accidental misconfiguration, not adversarial attacks. When ospfIfAuthKey is read via SNMP, it always returns a zero-length octet string to prevent key disclosure.
The NSSA translator state machine (ospfAreaNssaTranslatorState) has three states: enabled (role set to 'always'), elected (candidate border router is actively translating type-7 LSAs to type-5), and disabled (candidate is not translating). Transitions are driven by NSSA translator election.
The OSPF interface state machine (ospfIfState) defines seven states: down, loopback, waiting, pointToPoint, designatedRouter, backupDesignatedRouter, and otherDesignatedRouter. Transitions are driven by link events and DR election results on multi-access networks; the default state is down.