reason for type 4 & 5 LSA appearnce in STUB Area

[athambi]

When I declare an area as a stub area in OSPF I see type 4 and type 5 LSA in that stub area.Ideally both the LSA should be blocked .

How ever when I declare it as a Total stub area type 3,4,5 are blocked .

Question is why Stub area is not blocking 4&5..What will be the probable causes ??

[leonvd79]

Hello athambi,

You have to be more specific.

Post your OSPF topology, database, process information and (partial) configuration.

Without this information we cannot give a useful answer other than misconfiguration on your behalf.

--Leon

[athambi]

Leon,

I have attached config from 3 routers.When I do a "show ip ospf database" in the router named NEWYORKBR which has area 2 as totally stub area I see that SUMMARY NET LINK STATES with a link id of 0.0.0.0. and the advertising router being self If my understanding is correct there should not be summary link state entry.

PLease clarify

NOte: Area 2 is a Totally stub area .I have attached the wrong config

NewYork-BR#show ip ospf database

OSPF Router with ID (10.23.17.2) (Process ID 100)

Router Link States (Area 0.0.0.0)

Link ID ADV Router Age Seq# Checksum Link count

10.23.17.2 10.23.17.2 507 0x80000006 0x756 1

10.24.17.1 10.24.17.1 513 0x8000000D 0xBBE4 2

10.24.17.2 10.24.17.2 757 0x80000006 0x76A4 1

Net Link States (Area 0.0.0.0)

Link ID ADV Router Age Seq# Checksum

10.23.17.1 10.24.17.1 513 0x80000008 0xC39F

10.24.17.1 10.24.17.1 819 0x80000002 0xCF97

Summary Net Link States (Area 0.0.0.0)

Link ID ADV Router Age Seq# Checksum

20.20.20.1 10.23.17.2 505 0x80000003 0x1CAC

Router Link States (Area 2)

Link ID ADV Router Age Seq# Checksum Link count

10.23.17.2 10.23.17.2 518 0x80000001 0xA83 1

Summary Net Link States (Area 2)

Link ID ADV Router Age Seq# Checksum

0.0.0.0 10.23.17.2 518 0x80000001 0x1BEE

NewYork-BR#

Please clarify my doubt

[leonvd79]

Helo Athambi,

The provided OSPF database does not show inconsistancies. The Summary Net Link States (LSA type 3) for area 2 display an injected default-route, that is the result of "area 2 stub no-summary" command.

From your configurations of Seattle and New York I can see no reason why LSA type 4 and 5 would be present in your OSPF database. I don't see them in the "show ip ospf databse" output you've pasted in your reply.

HTH

--Leon

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[athambi]

Hello Leon,

Thanks. I am only talking about NEWYORKBR router.The Loop back interface of this router belong to TOTALLY STUB area and I execute the command " show ip ospf database" in NEWYORKBR .As per Totally stub area rules it wont allow LSA 3,4,5,But in this case I guess you can see that a just one Summary Net link State is appearing in OSPF database,Is this a correct behaviour,if so why ?.

Please note in NEWYORKBR loopback interface is the one that belongs to Area 2 which is a Totally stub area .

Aj

[leonvd79]

Hello Aj,

Like I said in my previous post, when a stub or totally stubby area is configured a default-route is injected into that area.

Take a look at the OSPF technote:

How OSPF Injects a Default Route into a Stub or Totally Stub Area

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00801ec9f7.shtml#totally

HTH

--Leon

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[athambi]

got it Thanks