OSPF Redistribution - default route missing

Unanswered Question
Sep 19th, 2012
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Hello,


I found the following scenarium:

Our customer has on ots core switches two ospf processes running.

One ospf process injects a default route. This default route should also redistributed into the other process. And therefore inject into te second backbone area.


The command "sh ip ospf process <1> database shows the o.o.o.o route

After redistribution :

Redistribute ospf 1 subnets metric-type 1


The default isn't in the second ospf database?! All other routes are redistributed?!


Any idea?


Thanks

Udo


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Peter Paluch Wed, 09/19/2012 - 22:10
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Hi Udo,


You can not redistribute a default route into OSPF, at least in Cisco's OSPF implementation. OSPF on Cisco devices specifically avoids redistributing the default route into OSPF. The only way to inject a default route into OSPF is to use the default-information originate command in the appropriate OSPF process.


Best regards,

Peter

udo.konstantin Thu, 09/20/2012 - 06:08
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Thank you Peter...


That is what I also thought...but please can you tell me where I can read this ? RFC ?!


Udo


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Peter Paluch Thu, 09/20/2012 - 06:45
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Hello Udo,


This behavior is not specified in any RFC to my best knowledge. It is an implementation choice made by Cisco. However, the following document


http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094374.shtml#route0.0


specifically states:


The default routes created using the ip route 0.0.0.0 0.0.0.0 command are not propagated by OSPF and IS-IS. Additionally, this default cannot be redistributed into OSPF or IS-IS using the redistribute command. Use the default-information originate command to generate a default route into an IS-IS or OSPF routing domain. For more detailed information on behavior of default routes with OSPF, refer to How Does OSPF Generate Default Routes?


Best regards,

Peter

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