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OSPF TYPE1 INTERNAL/EXTERNAL

Hi,

Could someone please let me know the difference between normal type1 LSA and external or internal type1 LSA?

MITHIL

mithil_r@rediffmail.com

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Re: OSPF TYPE1 INTERNAL/EXTERNAL

There are a few types of LSAs in OSPF:

-- Type 1, stub network

-- Type 2, transit network

These are the LSAs generated by a router to describe the networks it's connected to, locally. They are only flooded throughout an area; they won't be flooded past an ABR. They are called intraarea routes.

-- Type 3, summary

This is the type that an ABR sends to routers outside an area describing what networks are reachable inside an area. They are called interarea routes.

-- Type 4, border router

The type 4 LSA is an odd bird, it's generated at the ABR to let routers outside the area know about the specific route to a particular source of external routes.

-- Type 5, external

This is an external route, a route that has been brought into OSPF from some other protocol, such as connected, static, EIGRP, etc.

There are two types of type 5's, an external type 1 and an external type 2 (and this may be what you are asking about?). An external type 1 carries a metric that is directly comparable to the interal OSPF metrics, while an external type 2 carries metrics that are not directly comparable to the internal OSPF metrics (though I may have them backwards). At any rate, the way they are implemented on most routers results in them being, pretty much, the same thing.

Now, going back to your original question, there is only one type 1, and it's only internal, stub networks. If you mean an external type 1, then this is really a type 5, external, type 1 metric within the type 5, if this makes sense.

:-)

Russ.W

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