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New Member

OSPF ASBR issue

The scheme of the network is on the picture. Router A supposes that router D is ABR/ASBR (review show ip ospf border-routers). And router A doesn't see router H as ASBR.

I've checked OSPF databases on routers A and D. Router D doesn't sent LSA type 4 into area 0.

Why router A doesn't suppose that ASBR is router H?

7 REPLIES
Cisco Employee

Re: OSPF ASBR issue

Andrew,

I looks like router D is redistributing external routes in OSPF, or at least is configured to do so.

As to why router H is not being seen as an ASBR, we would need to see the configuration to find out. Can you please post the ospf configuration for router D and H.

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: OSPF ASBR issue

Router D isn't configured to do redistribution. You can find some more 'show' commands in attachements.

New Member

Re: OSPF ASBR issue

Frm rtrD to rtrH issue the following commands

1) Sh ip ospf interface

2) Sh ip ospf data

3) Sh ip ospf neighbor

Could you post some of the output to further investigate. Thanks

Re: OSPF ASBR issue

Bear in mind your use of areas - you will not see detail from within area 20 in area 0. H is in area 20, D is the ABR between 20 & 0, A is in the backbone.

New Member

Re: OSPF ASBR issue

You're right. You've described my situation correctly.

I've attached some more 'show' commands to gain a better understanding.

Cisco Employee

Re: OSPF ASBR issue

Andrew,

The reason router D is being seen as both an ABR and an ASBR is that you configured area 20 as NSSA. Router D does the type 7 to type 5 translation and is therefore considered as the ASBR for these external routes.

It is also normal in this case that router H is not seen as an ASBR outside of area 20.

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: OSPF ASBR issue

I think that ABR (router D) must send LSA type 4 about ASBRs situated in his area (area 20). But router A doesn't see any LSA type 4. Why? Please correct me, if I'm not right.

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