OSPF Area information in LSDB.

Unanswered Question
Sep 27th, 2007

hi

we are having more than 25 routers running ospf .and there are 4 different stub areas.namely 10,20,30 and 40.

Routers connected to these areas are R1, R2 , R3 and R4 respectively. These are ABR.

These routers are connected to other locations in stub area by Channelised E1.

R1 has a subnet 10.1.0.0 / 16 in stub area 10

R2 has a subnet 10.2.0.0 / 16 in stub area 20

R3 has a subnet 10.3.0.0 / 16 in stub area 30

R4 has subnet 10.4.0.0 / 16 in stub area 40

Now if I need to know from any of the router is network which subnets are learned from which area

What is the command that will tell us that this subnet is learned from this router and from this area

will sho ip ospf database will display these details

Thanx in advance

Subodh

I have this problem too.
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JORGE RODRIGUEZ Thu, 09/27/2007 - 14:22

Hi Subodh, if I understand your question correctly you want to find out what routes are being learned from the stub area sites.. if this is what you are looking for you can use "show ip route " in each site abr router.You may also use "show ip ospf database " to reference ospf LSDB/link state database, which will show all types of routes in more specific way in terms of which router is advertizing what networks.

The link state database is periodically updated throughout all routers withing the OSPF domain, so what you see in the database are routes reachable throughout your internal network.

let us know If this is the information you were indeed looking for.

If looking for any other information here is a link for ospf support page or just drop a line with question.

http://www.cisco.com/en/US/tech/tk365/tk480/tsd_technology_support_sub-protocol_home.html

HTH

Jorge

Kevin Dorrell Thu, 09/27/2007 - 14:30

As far as I am aware, the database contains inter-area routes and a reference to the border router only. Only the border router itself knows the identity of the area it learned he route from.

What I am saying, I guess, is that the Type-3 LSA does not contain the originating area, only the reference to the originating ABR.

Kevin Dorrell

Luxembourg

GillieLucent Fri, 09/28/2007 - 10:12

Actually, area number is useful only within that particular area.If both sender and receiver are in same area, then only they form neighbourship.

Within the area, LSAs are idetified by originator. Outside the area LSAs are adveritised by the ABR.

Even, you can have two areas with same area number.

If you want to know the adveritiser, below are the commands :

show ip ospf database router - to see router LSAs

show ip ospf database network - to see network LSAs

show ip ospf database summary - to see summary LSAs

show ip ospf database asbr-summary - to see ASBR summary LSAs

show ip ospf database external - to see external LSAS

See the 'OSPF Database Example' of the below link :

http://cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml

for examples.

Thanks,

Vijaybabu

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