OSPF Discovery

The OSPF Topology Updater provides OSPF OnmsTopology, consolidating OSPF data the OSPF Collector collects. Only full bidirectional connections between two OSPF-supported devices become edges. Node A and Node B are connected by an OSPF edge if and only if there is an OSPF link in Node A to Node B and vice versa.

The following MIBSs are supported to discover and build the OSPF network topology and are collected by the OSPF Discovery Collector.

The relevant MIBs for OSPF topology are OSPF-MIB and OSPF-TRAP-MIB. These MIBs define the relevant objects used to find OSPF links, specifically the router ID. In OSPF, the router ID has the same format as an IP address, but identifies the router independent of its IP address.

All the interfaces are identified by their IP addresses. The OSPF links come from the SNMP ospfNbrTable defined in OSPF-MIB. This table is persisted in the ospfLink table:

Table 1. Supported OIDs from OSPF-MIB
Name	Description	OID
ospfRouterId	A 32-bit integer uniquely identifying the router in the autonomous system. By convention, to ensure uniqueness, this should default to the value of one of the router’s IP interface addresses. This object is persistent and when written the entity should save the change to non-volatile storage.	.1.3.6.1.2.1.14.1.1.0
ospfAdminStat	The administrative status of OSPF in the router. The value `enabled` indicates the OSPF process is active on at least one interface; `disabled` disables it on all interfaces. This object is persistent and when written the entity should save the change to non-volatile storage.	.1.3.6.1.2.1.14.1.2.0
ospfVersionNumber	The current version number of the OSPF protocol is 2.	.1.3.6.1.2.1.14.1.3.0
ospfAreaBdrRtrStatus	A flag to note whether this router is an area border router.	.1.3.6.1.2.1.14.1.4.0
ospfAreaASBdrRtrStatus	A flag to note whether this router is configured as an autonomous system border router. This object is persistent and when written the entity should save the change to non-volatile storage.	.1.3.6.1.2.1.14.1.5.0
ospfIfIpAddress	The IP address of this OSPF interface.	.1.3.6.1.2.1.14.7.1.1
ospfAddressLessIf	To ease the instancing of addressed and addressless interfaces; this variable takes the value 0 on interfaces with IP addresses and the corresponding value of `ifIndex` for interfaces having no IP address.	.1.3.6.1.2.1.14.7.1.2
ospfNbrIpAddr	The IP address this neighbor uses in its IP source address. Note that on addressless links, this will not be 0.0.0.0 but the address of another of the neighbor’s interfaces.	.1.3.6.1.2.1.14.10.1.1
ospfNbrAddressLessIndex	On an interface having an IP address, zero. On addressless interfaces, the corresponding value of `ifIndex` in the Internet Standard MIB. On row creation, this can be derived from the instance.	.1.3.6.1.2.1.14.10.1.2
ospfNbrRtrId	A 32-bit integer (represented as a type IpAddress) uniquely identifying the neighboring router in the autonomous system.	.1.3.6.1.2.1.14.10.1.3

Table 2. Supported OIDs from IP-MIB
Name	Description	OID
ipAdEntIfIndex	The index value that uniquely identifies the interface to which this entry applies. The interface identified by a particular value of this index is the same interface as identified by the same value of the `IF-MIB’s ifIndex`.	.1.3.6.1.2.1.4.20.1.2
ipAdEntNetMask	The subnet mask associated with the IPv4 address of this entry. The value of the mask is an IPv4 address with all the network bits set to 1 and all the host bits set to 0.	.1.3.6.1.2.1.4.20.1.3

Find generic information about the OSPF link discovery process in the OSPF information box on the node detail page of the device. Information gathered from these OIDs is stored in the following database table:

Figure 1. Database tables related to OSPF discovery