Information Technology Reference
In-Depth Information
The characteristics of OSPFv2 follow:
Link-state routing protocol.
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Uses IP protocol 89.
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Classless protocol (supports VLSMs and CIDR).
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Metric is cost (based on interface bandwidth by default).
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Fast convergence. Uses link-state updates and SPF calculation.
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Reduced bandwidth use. Sends partial route updates only when changes occur.
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Routes are labeled as intra-area, interarea, external Type 1, or external Type 2.
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Support for authentication.
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Uses the Dijkstra algorithm to calculate the SPF tree.
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Default administrative distance is 110.
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Uses multicast address 224.0.0.5 (ALLSPFRouters).
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Uses multicast address 224.0.0.6 (ALLDRouters).
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Good scalability. Recommended for large networks.
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RFC 2740 describes OSPF Version 3 as a routing protocol for IPv6 networks. Note that
OSPFv3 is for IPv6 networks only and that it is not backward compatible with OSPFv2
(used in IPv4). OSPF algorithms and mechanisms, such as flooding, router types, desig-
nated router election, areas, stub and NSSA, and SPF calculations, remain the same.
Changes are made for OSPF to support IPv6 addresses, address hierarchy, and IPv6 for
transport. OSPFv3 uses multicast group FF02::5 for all OSPF routers and FF02::6 for all
designated routers.
OSPFv3 Changes from OSPFv2
The following are the major changes for OSPFv3:
Version number is 3:
Obviously, this is a newer version of OSPF, and it runs over
IPv6 only.
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Key
To p i c
Support for IPv6 addressing:
New LSAs created to carry IPv6 addresses and
prefixes.
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Per-link processing:
OSPFv2 uses per-subnet processing. With link processing,
routers in the same link can belong to multiple subnets.
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Address semantics removed:
Addresses are removed from the router and network
LSAs. These LSAs now provide topology information.
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No authentication in the OSPFv3 protocol:
schemes inherited in IPv6.
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