From: zzk (ccie_99@yahoo.com)
Date: Tue Dec 09 2003 - 07:58:49 GMT-3
Hello
Thanks for the illustration, Brian.
Our problem is there is a ABR router R1 generating a
IA type default route into the network (because the
area is totally stub NSSA), and another ASBR R2
generating a external type default route.
All the routers chose R1 as the default gateway,
because LSA type 3 is prefered over LSA type 7.
Is there anyway we can make the routers to select R2
as the default gateway?
There is one ABR LSA type 3 filtering feature, however
it is not avaliable on Cat6 MSFC. :(
thanks
--- Brian McGahan <bmcgahan@internetworkexpert.com>
wrote:
> A not-so-totally-stubby area (nssa no-summary) is a
> totally stubby
> area that you can redistribute into. The ABR of the
> NSTSA automatically
> originates a default of LSA type-3 into the area:
>
> Rack1R1#sh run | b router ospf
> router ospf 1
> area 12 nssa
> network 12.0.0.1 0.0.0.0 area 12
>
> Rack1R2#sh run | b router ospf
> router ospf 1
> area 12 nssa no-summary
> network 12.0.0.2 0.0.0.0 area 12
> network 150.1.2.2 0.0.0.0 area 0
>
> Rack1R1#show ip route ospf
> O*IA 0.0.0.0/0 [110/11] via 12.0.0.2, 00:02:49,
> Ethernet0/0
> Rack1R1#show ip ospf database
>
> OSPF Router with ID (150.1.1.1) (Process
> ID 1)
>
> Router Link States (Area 12)
>
> Link ID ADV Router Age Seq#
> Checksum Link count
> 150.1.1.1 150.1.1.1 188
> 0x80000002 0x0006CE 1
> 150.1.2.2 150.1.2.2 188
> 0x80000003 0x00F8D2 1
>
> Net Link States (Area 12)
>
> Link ID ADV Router Age Seq#
> Checksum
> 12.0.0.2 150.1.2.2 189
> 0x80000001 0x001342
>
> Summary Net Link States (Area 12)
>
> Link ID ADV Router Age Seq#
> Checksum
> 0.0.0.0 150.1.2.2 211
> 0x80000001 0x00CBCE
>
>
> An NSSA for which the ABR originates a default is
> different (nssa
> default-information-originate). This is an LSA
> type-7 default (N1 or N2, N2
> by default):
>
> Rack1R2#sh run | b router ospf
> router ospf 1
> log-adjacency-changes
> area 12 nssa default-information-originate
> network 12.0.0.2 0.0.0.0 area 12
> network 150.1.2.2 0.0.0.0 area 0
>
> Rack1R1#sh ip route ospf
> 150.1.0.0/16 is variably subnetted, 3 subnets,
> 2 masks
> O IA 150.1.2.2/32 [110/11] via 12.0.0.2,
> 00:00:46, Ethernet0/0
> O*N2 0.0.0.0/0 [110/1] via 12.0.0.2, 00:00:42,
> Ethernet0/0
> Rack1R1#sh ip ospf database
>
> OSPF Router with ID (150.1.1.1) (Process
> ID 1)
>
> Router Link States (Area 12)
>
> Link ID ADV Router Age Seq#
> Checksum Link count
> 150.1.1.1 150.1.1.1 568
> 0x80000002 0x0006CE 1
> 150.1.2.2 150.1.2.2 568
> 0x80000003 0x00F8D2 1
>
> Net Link States (Area 12)
>
> Link ID ADV Router Age Seq#
> Checksum
> 12.0.0.2 150.1.2.2 569
> 0x80000001 0x001342
>
> Summary Net Link States (Area 12)
>
> Link ID ADV Router Age Seq#
> Checksum
> 150.1.2.2 150.1.2.2 54
> 0x80000001 0x00EF0F
>
> Type-7 AS External Link States (Area
> 12)
>
> Link ID ADV Router Age Seq#
> Checksum Tag
> 0.0.0.0 150.1.2.2 50
> 0x80000001 0x0040C7 0
>
>
>
>
> Brian McGahan, CCIE #8593
> bmcgahan@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987
> Direct: 708-362-1418 (Outside the US and Canada)
>
>
> > -----Original Message-----
> > From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of
> > Scott Morris
> > Sent: Monday, December 08, 2003 11:46 AM
> > To: 'zzk'; ccielab@groupstudy.com
> > Subject: RE: how to filter out default route in
> OSPF totally stub area?
> >
> > Well, I'll be damned. Just when you think an RFC
> makes sense. :)
> >
> > However, the nssa default-info is the command that
> must be manually
> > done. And when you set up the "no-summary"
> version, I don't believe
> > that automatically generates a 0/0 route, it just
> prevents other IA
> > routes from coming in. So that leaves you with
> NEEDING to manually
> > configure the "nssa default-info" command.
> >
> > Either way you go there, it still seems to be an
> administratively
> > controlled feature.
> >
> >
> > Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service
> Provider) #4713,
> > CISSP, JNCIS, et al.
> > IPExpert CCIE Program Manager
> > IPExpert Sr. Technical Instructor
> > swm@emanon.com/smorris@ipexpert.net
> > http://www.ipexpert.net
> >
> >
> > -----Original Message-----
> > From: zzk [mailto:ccie_99@yahoo.com]
> > Sent: Monday, December 08, 2003 9:33 AM
> > To: swm@emanon.com; ccielab@groupstudy.com
> > Subject: RE: how to filter out default route in
> OSPF totally stub area?
> >
> >
> > Hi Scott
> > Thanks for your reply.
> > I think there is nssa totally stub areas. You can
> see
> > it at
> >
>
http://www.cisco.com/en/US/tech/tk365/tk480/technologies_tech_note09186a
> > 0080094a88.shtml#definestub
> >
> > The exit point of the whole network is inside this
> > area 1, so this ASBR has to generate default route
> for
> > the whole network. However we are trying to reduce
> the
> > number of LSAs in this area 1, thats why we also
> want
> > to use totally stub area.
> >
> > I hope you understand the senario, and appreciate
> if
> > there is any better idea.
> >
> > regards
> > --- Scott Morris <swm@emanon.com> wrote:
> > > If your area is "totally stub" then it is NOT
> > > "nssa". If it is "nssa",
> > > then it is NOT "totally stub". You have to
> choose
> > > one or the other. If
> > > you are configuring it as an nssa, then you have
> to
> > > add a specific
> > > command to generate a default route, it's not in
> > > there automatically.
> > >
> > > If you are a totally stubby area, it's generated
> automatically. If
> > > you don't want it to do that because there is
> more than
> > > one exit point, then
>
=== message truncated ===
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This archive was generated by hypermail 2.1.4 : Sat Jan 03 2004 - 08:25:38 GMT-3