Ospf Network Type - H3C S5600 Series Operation Manual

Operation Manual – Routing Protocol
H3C S5600 Series Ethernet Switches
If this feature is configured on an ABR, the ABR will summarize Type-5 LSAs
translated from Type-7 LSAs.
VII. Route types
OSPF prioritizes routes into four levels:
Intra-area route
Inter-area route
type1 external route
type2 external route
The intra-area and inter-area routes describe the network topology of the AS, while
external routes describe routes to destinations outside the AS. OSPF classifies
external routes into two types: type1 and type2.
A type1 external route is an IGP route, such as a RIP or static route, which has high
credibility and whose cost is comparable with the cost of an OSPF internal route. The
cost from a router to the destination of the type1 external route= the cost from the
router to the corresponding ASBR+ the cost from the ASBR to the destination of the
external route.
A type2 external route is an EGP route, which has low credibility, so OSPF considers
the cost from the ASBR to the destination of the type2 external route is much bigger
than the cost from the ASBR to an OSPF internal router. Therefore, the cost from the
internal router to the destination of the type2 external route = the cost from the ASBR
to the destination of the type2 external route. If two routes to the same destination
have the same cost, then take the cost from the router to the ASBR into consideration.

4.1.5 OSPF Network Type

I. Four OSPF network types
OSPF divides networks into four types by link layer protocols:
Broadcast: If Ethernet or FDDI is adopted, OSPF defaults the network type to
broadcast. In a broadcast network, protocol packets are sent in multicast
(224.0.0.5 and 224.0.0.6) by default.
Non-broadcast multi-access (NBMA): If Frame Relay, ATM, or X.25 is adopted,
OSPF defaults the network type to NBMA. In an NBMA network, protocol
packets are sent in unicast.
Point-to-multipoint (P2MP): OSPF will not default the network type of any link
layer protocol to P2MP. A P2MP network must be compulsorily changed from
another network type. The common practice is to change an NBMA network into
a P2MP network. In a P2MP network, protocol packets are sent to the multicast
address (224.0.0.5) by default, but protocol packets can be sent in the unicast
address as needed.
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Chapter 4 OSPF Configuration