Excellent post Marko understood now ......huh!!!!!!!! took some time to digest after some experimentation
the Key point here is RID of ASBR may *not be a routable ip add*, or if a routable ip add may not be advertised in ospf via network command and hence when external routes travels to other areas the advertising router is still ASBR RID and other areas dont know how to reach that RID but ABR knows about the RID of ASBR via TYPE 1 LSA CONCLUSION: if the RID is Non Routable IP Add NO LSA Type 4 is needed basically if the RID is a Routable ip add it will be known to other areas via Type 3 LSA and Type 4 both Thanks all.......for helping out GoodLuck !!!! On Wed, Aug 15, 2012 at 12:49 PM, Marko Milivojevic <[email protected]>wrote: > Manish, > > Have you read the series of articles I wrote on OSPF LSA types? > > > http://blog.ipexpert.com/2010/08/11/quick-look-into-ospf-database-router-lsa/ > > http://blog.ipexpert.com/2010/09/13/quick-look-into-ospf-database-network-lsa/ > > http://blog.ipexpert.com/2010/09/15/quick-look-into-ospf-database-summary-lsa/ > > http://blog.ipexpert.com/2010/09/22/quick-look-into-ospf-database-external-and-asbr-summary-lsa/ > > http://blog.ipexpert.com/2010/09/27/quick-look-into-ospf-database-nssa-external-lsa/ > > There's also a pretty good series written by Joe Astorino on our blog > that talks specifically about Type 4 LSA: > > > http://blog.ipexpert.com/2009/11/04/ospf-type-4-lsa-the-forward-address-part-1/ > > http://blog.ipexpert.com/2009/11/11/ospf-type-4-lsa-the-forward-address-part-2/ > > -- > Marko Milivojevic - CCIE #18427 (SP R&S) > Senior CCIE Instructor - IPexpert > > On Tue, Aug 14, 2012 at 6:40 AM, MANISH <[email protected]> > wrote: > > Hi All, > > > > can some one please explain me the difference in LSA Type 3 and LSA Type > 4 > > > > as per my understanding > > > > LSA Type 3 is used for inter area routes ........meaning all the Type 1/2 > > inside an area when crosses in to other area will be advertised using > type > > 3 > > > > LSA Type 4 is the IP address of ASBR. > > > > my confusion is if we already know about ip add of ASBR through Type 3 > > since every thing gets flooded in to other areas why do we need type 4 > > explicitly to define ip add of ASBR. > > > > > > I read many blogs and other sources but still could not undersdtand. > > > > take a look at this blog explanation, will fa0/0 of R6 not be known to > > other areas using type 3 lsa ? > > > > > http://blog.ipexpert.com/2009/11/04/ospf-type-4-lsa-the-forward-address-part-1/ > > > > > > > > Thank You. > > Manish > > _______________________________________________ > > For more information regarding industry leading CCIE Lab training, > please visit www.ipexpert.com > > > > Are you a CCNP or CCIE and looking for a job? Check out > www.PlatinumPlacement.com > > > > http://onlinestudylist.com/mailman/listinfo/ccie_rs > _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com http://onlinestudylist.com/mailman/listinfo/ccie_rs
