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OSPFv3 Introduction

 

So far we have covered OSPFv2 in great detail. Lets have a look at OSPFv3 now, but why do we need two versions of a protocol ?

Well the answer is simple – because of network evolutions, more and more networks are going towards IPv6 (or IPv4+IPv6). OSPF was initially designed for IPv4 and could not handle IP6 natively. So OSPFv3 comes as a solution.
Keep in mind OSPFv3 supports both IPv4 and IPv6 while OSPFv2 supported only IPv4. Both versions are not compatible with each other.

So Few things were added/modified in OSPFv3 :-
1. It has “links” instead of “network”, i.e. SPT is now per link and free of subnets.
2. Since IPv4 and IPV6 has different prefix architecture, OSPFv3 packets headers were made free of any prefix (remember 225.0.0.5 & 225.0.0.6). Now prefixes are carried as LSA payload (remember ISIS).
3. Some new LSA were defined/modified, more on them later.
4. Router ID is now need to be manually assigned.
5. Authentication is removed (because of IPv6 supports native IPsec).
6. OSPFv3 communicates over link local IPv6 address, so no common subnet requirement to be neighbour. This is because IPv6 supports multiple subnets over single interface.

Now Coming to OSPFv3 LSAs lets have a quick look on them :-

LSA OSPPv2 OSPFv3
LSA 1 Router LSA Router LSA
LSA 2 Network LSA Network LSA
LSA 3 Network Summary LSA Interarea prefix LSA
LSA 4 ASBR Summary LSA Interarea Router LSA
LSA 5 External LSA External LSA
LSA 7 NSSA NSSA
LSA 8 External Attributes LSA Link LSA
LSA 9 link-local “opaque” Intera area prefix LSA

We will discuss them in great details. Stay Tuned…

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