Re: Type-4 LSA and NSSA

Hey narbick,
                You said that you will se an LSA type 3 in area 2 , why we
didn't see LSA type 4 on area 0 ?

Thanks

On Sat, May 9, 2009 at 5:22 AM, Narbik Kocharians <narbikk_at_gmail.com> wrote:

> I agree with Scott, but look at the following scenario:
>
> Area 0 ------ Area 1
>
> If area 1 has an ASBR and its configured as an NSSA, none of the routers in
> the entire domain will see LSA type 4. Whereas,
>
> Area 2 ------ Area 0 ------ Area 1
>
> You will see an LSA type 4 in Area 2.
>
> On Fri, May 8, 2009 at 5:57 PM, Scott Morris <
> smorris_at_internetworkexpert.com
> > wrote:
>
> > Type 4's are used for next hop reachability to get to the Type 5 LSAs
> > (ASBR). If you have no Type 5's, you have zero need for a Type 4 LSA.
> :)
> >
> > So I'd suggest that someone messed up in the book?
> >
> >
> >
> >
> > *Scott Morris*, CCIE/x4/ (R&S/ISP-Dial/Security/Service Provider) #4713,
> >
> > JNCIE-M #153, JNCIS-ER, CISSP, et al.
> >
> > JNCI-M, JNCI-ER
> >
> > smorris_at_internetworkexpert.com
> >
> >
> > Internetwork Expert, Inc.
> >
> > http://www.InternetworkExpert.com <http://www.internetworkexpert.com/> <
> http://www.internetworkexpert.com/>
> >
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> >
> >
> >
> > Mike Leske wrote:
> > > Hi group,
> > >
> > > can someone please give a hint on this?
> > >
> > > I have problems to understand why OSPF LSA Type-4 should be allowed
> > within
> > > NSSA's.
> > >
> > > According to Routing TCP/IP, Vol. 1, page 389, Type-4 LSA's are allowed
> > to
> > > be sent into NSSA's.
> > > Cisco (
> > >
> >
> http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a88.shtml
> > )
> > > gives a similar description:
> > > After you define Area 1 as an NSSA, it must have these characteristics:
> > > - No Type 5 LSAs are allowed in Area 1
> > >
> > > Cisco further defines Type-3 and Type-4 LSA's are not sent into Totally
> > > NSSA's.
> > >
> > > Does it make sense?
> > > As we know, LSA Type-4 describe ASBR's; but if the information about
> > > external routes is blocked, there's no need to have Type-4 LSA's.
> > >
> > > When I Lab this up, the NSSA router indeed has NO Type-4 LSA pointing
> to
> > an
> > > ASRB within Area 0.
> > >
> > > Thus, in which scenario will I ever see Type-4 LSA's within a NSSA?
> > >
> > > Thanks in advance.
> > >
> > > Mike
> > >
> > >
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>
> --
> Narbik Kocharians
> CCSI#30832, CCIE# 12410 (R&S, SP, Security)
> www.MicronicsTraining.com <http://www.micronicstraining.com/>
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Received on Sat May 09 2009 - 09:32:29 ART