Default-information originated

[csco10716389]

Can any body help me the exact use of Default-information originated incase of OSPF

[senthil_kumarpv]

By using that command, if any static default route is there ,it will redistribute in the OSPF

[Joseph W. Doherty]

BTW:

There's also an option to inject a default even if there's no default known to the router.

"Q. Can an OSPF default be originated into the system based on external information on a router that does not itself have a default?

A. OSPF generates a default only if it is configured using the command default-information originate and if there is a default network in the box from a different process. The default route in OSPF is 0.0.0.0. If you want an OSPF-enabled router to generate a default route even if it does not have a default route itself, use the command default-information originate always."

[csco10716389]

Still the matter is not clear can u please Explain me putting a scenario.

[s.arunkumar]

In simple words,an ospf ASBR cannot generate a default route,ie ,even if the other IGP running at ASBR(say,eigrp,rip etc) has got a default route,while redistributing these protocols ,by default ,the default routes are not injected into the ospf domain..So u require to give default-information originate command..

This command requires an explicit entry of default route in the routing table..

Eg: R1----R2----R3

Now eigrp is running between R1 and R2 and ospf between R2 and R3.If R2 has got a default route learned via eigrp.When redistributing eigrp into ospf this default route is not propogated into ospf domain,ie,towards R3.In order to do so u need to configure default-information originate under ospf process.

Additionaly,this can also be used by nssa abr to inject type 7 default routes into nssa area.This does not require the default route to be explicitly present in routing table.

Hope this clears...

arun

[csco10716389]

Thanks Arun its clear now.thanks once again.

[Joseph W. Doherty]

Some Cisco documents might also further clarify.

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00801ec9f0.shtml

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a74.shtml

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00801ec9fa.shtml

What the above will show is getting a default route into normal area vs. NSSA area. You can have the latter without the former. Also, think they show you don't actually have to redistribute other external routes into OSPF to redistribute an externally known default, nor even need an externally known default at all.