From: NET HE (he_net@hotmail.com)
Date: Wed Sep 12 2007 - 00:35:03 ART
I have labbed it up. My result is different from you.
At R5, O*N2 0.0.0.0/0 next hop is R7; at R7, O*N2 0.0.0.0/0 next hop is R8.
The result makes sense to me. First, the default route injected into NSSA
has type 2 metric, which doesn't change metric value throughout the ospf
domain. Secondly, this is NSSA area, therefore, ASBR type-7 is preferrable
over ABR type-7 routes (tie breaker).
Best Regards,
Net (Xin) He
>X-OriginalArrivalTime: 12 Sep 2007 02:59:12.0966 (UTC)
>FILETIME=[E5E0E660:01C7F4E8]
>
>Hi NET HE,
>
>I have labbed it up. My topo as follows:
>
> -----Area0----- R5 -----Area 1 NSSA----- R7 -----Area 1 NSSA----- R8
>
>R5 & R8 both have the "area 1 nssa default-information-originate" command.
>R8 does not source the N2 default route until I configured a static default
>route on it. You are right.
>
>R5-R7 is FastEthernet. R7-R8 is a serial link.
>
>
>R5#sh ip os da
> Type-7 AS External Link States (Area 1)
>
>Link ID ADV Router Age Seq# Checksum Tag
>0.0.0.0 5.5.5.5 713 0x80000001 0x00EADD 0
>0.0.0.0 8.8.8.8 811 0x80000001 0x002830 0
>
>R5#sh ip os b
>i 8.8.8.8 [65] via 150.50.7.7, FastEthernet0/0, ASBR, Area 1, SPF 11
>
>
>R7#sh ip os da
> Type-7 AS External Link States (Area 1)
>
>Link ID ADV Router Age Seq# Checksum Tag
>0.0.0.0 5.5.5.5 852 0x80000001 0x00EADD 0
>0.0.0.0 8.8.8.8 950 0x80000001 0x002830 0
>
>R7#sh ip os b
>i 8.8.8.8 [64] via 150.50.5.69, Serial0/0, ASBR, Area 1, SPF 4
>i 5.5.5.5 [1] via 150.50.7.5, FastEthernet0/0, ABR/ASBR, Area 1, SPF 4
>
>
>Examing their routing tables, R5 learns O*N2 0.0.0.0/0 from R7. R7 learns
>O*N2 0.0.0.0/0 from R5! I believe this is due to R7 choosing the lowest
>cost
>to the advertising ASBR since it's an External Type-2 route. Obviously
>routing loop is formed between R5-R7 for external addresses.
>
>Any comments?
>
>
>Thank you.
>
>B.Rgds,
>Lim TS
>
>
>On 9/11/07, NET HE <he_net@hotmail.com> wrote:
> >
> > - ASBR does need have a default route first, then inject type-7 default
> > route into NSSA area. And depends on metric-type, it can be N1 or N2.
> > (nssa
> > default-information originate)
> > - ABR unconditionally inject a default route using "nssa
> > default-information
> > originate), it is a type-7 LSA as well.
> > - ABR unconditionally inject a default route using "nssa no-summary",
>but
> > it
> > is a type-3 LSA.
> >
> > Best Regards,
> > Net (Xin) He
> >
> > >X-OriginalArrivalTime: 11 Sep 2007 02:07:27.0120 (UTC)
> > >FILETIME=[803CA900:01C7F418]
> > >
> > >Hi NET HE,
> > >
> > >Thanks for your reply.
> > >
> > >I have never tried configuring "area X nssa
> > default-information-originate"
> > >on an internal router (non-ABR) in an NSSA. When used on the ABR, it
> > >unconditionally sources an N2 default route into the NSSA by default.
>If
> > >applied on an internal router in the NSSA, does the router have to have
>a
> > >default route (static route or learned from other IGP) in order to
>inject
> > >the Type-7 default?
> > >
> > >
> > >
> > >Thank you.
> > >
> > >B.Rgds,
> > >Lim TS
> > >
> > >
> > >
> > >On 9/11/07, NET HE <he_net@hotmail.com> wrote:
> > > >
> > > > In addition, cmd "area 23 nssa no-summary" can only be used at ABR
> > > > routers,
> > > > but cmd "area 23 nssa defalut-information-originate" can be used at
> > ABR
> > > > routers or ASBR routers, which are located in NSSA area, and inject
> > >type-7
> > > > LSA.
> > > >
> > > >
> > > > Best Regards,
> > > > Net (Xin) He
> > > >
> > > > >X-OriginalArrivalTime: 10 Sep 2007 23:08:20.0266 (UTC)
> > > > >FILETIME=[7A9CE0A0:01C7F3FF]
> > > > >
> > > > >with the "no-summary" option, the ABR will inject a default route
>and
> > > > >it will also block all LSA type 3s, therefore, the routers in the
> > NSSA
> > > > area
> > > > >will NOT see the inter-area routes. But with the
> > "default-information"
> > > > >keyword, the ABR will inject a default route but it won't block LSA
> > >type
> > > > 3s
> > > > >and as a result of that the routers within the NSSA area will still
> > > > >maintain
> > > > >LSA type 3s (Inter-Area routes).
> > > > >
> > > > >On 9/10/07, Carlos Trujillo Jimenez <nergal888@hotmail.com> wrote:
> > > > > >
> > > > > > Hi all.
> > > > > >
> > > > > > I have a NSSA area, the routers from the NSSA dont need
> > reachability
> > > > > > information about the external prefixes, that means I must
>inject
> > a
> > > > > > default
> > > > > > route for the external prefixes reachability.
> > > > > >
> > > > > > I have two options to do it.
> > > > > >
> > > > > > at the area border router:
> > > > > >
> > > > > > area 23 nssa no-summary
> > > > > >
> > > > > > or
> > > > > >
> > > > > > area 23 nssa defalut-information-originate
> > > > > >
> > > > > > Is there any significant difference between both options?? both
> > > > works,
> > > > >by
> > > > > > a
> > > > > > show ip route at the internal routers of the nssa area I can see
> > an
> > > > > > external
> > > > > > IA default route with both commands, theres is no difference,
>any
> > > > ideas
> > > > > > when
> > > > > > one of these options can and cannot be used???
> > > > > >
> > > > > >
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