From: bipin.atyale@hotmail.com
Date: Mon Jan 14 2008 - 10:28:09 ARST
The command area 1 nssa default-information-originate doesnt have always keyword.That you know very well.
This command is mainly intended for causing the ABR to advertise a default route into the NSSA.
While command default-information originate always is a specialised form of the redistribute command causing a default route to be
redistributed into OSPF or IS-IS.It also informs OSPF router that it is an ASBR.This default route is advertised using
Type 5 LSA.This command redistributes the already advertised default route into OSPF domain.Which in case of flapping
is still rerained in routing table because of always option.
But the default route advertised by area nssa command is the one created by LSA 3 or LSA 7 in case of NSSA for
provisioning outer areas access by default route to inner routers of NSSA area.Which could not get flapped at all as it is not a defined route.
Meaning the NSSA will always retain default route unless & untill it is blocked using no-redistribution option.
And Type 5 default routes will depend on the keyword "always".
Cheers
Bipin Atyale
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