3.13. OSPF Route Table Use

--  OSPF Use of the CIDR Route Table

ospfRouteGroup           OBJECT IDENTIFIER ::= { ospf 13 }

-- The IP Forwarding Table defines a number of objects for use by
-- the routing protocol to externalize its information.  Most of
-- the variables (ipForwardDest, ipForwardMask, ipForwardPolicy,
-- ipForwardNextHop, ipForwardIfIndex, ipForwardType,
-- ipForwardProto, ipForwardAge, and ipForwardNextHopAS) are
-- defined there.

-- Those that leave some discretion are defined here.

-- ipCidrRouteProto is, of course, ospf (13).

-- ipCidrRouteAge is the time since the route was first calculated,
-- as opposed to the time since the last SPF run.

-- ipCidrRouteInfo is an OBJECT IDENTIFIER for use by the routing
-- protocol.  The following values shall be found there depending
-- on the way the route was calculated.

ospfIntraArea      OBJECT IDENTIFIER ::= { ospfRouteGroup 1 }
ospfInterArea      OBJECT IDENTIFIER ::= { ospfRouteGroup 2 }
ospfExternalType1  OBJECT IDENTIFIER ::= { ospfRouteGroup 3 }
ospfExternalType2  OBJECT IDENTIFIER ::= { ospfRouteGroup 4 }

-- ipCidrRouteMetric1 is, by definition, the primary routing
-- metric.  Therefore, it should be the metric that route
-- selection is based on.  For intra-area and inter-area routes,
-- it is an OSPF metric.  For External Type 1 (comparable value)
-- routes, it is an OSPF metric plus the External Metric.  For
-- external Type 2 (non-comparable value) routes, it is the
-- external metric.

-- ipCidrRouteMetric2 is, by definition, a secondary routing
-- metric.  Therefore, it should be the metric that breaks a tie
-- among routes having equal metric1 values and the same
-- calculation rule.  For intra-area, inter-area routes, and
-- External Type 1 (comparable value) routes, it is unused.  For
-- external Type 2 (non-comparable value) routes, it is the metric
-- to the AS border router.

-- ipCidrRouteMetric3, ipCidrRouteMetric4, and ipCidrRouteMetric5 are
-- unused.