From: Toh Soon, Lim (tohsoon28@gmail.com)
Date: Sun Aug 26 2007 - 19:09:35 ART
Hi Serhat,
Below are sequence of commands I typed on the ABR (R4):
(1) With no summarization or Type-3 LSA filtering:
Summary Net Link States (Area 4)
Link ID ADV Router Age Seq# Checksum
192.168.10.0 200.0.0.4 1182 0x80000002 0x00DD0E
192.168.25.0 200.0.0.4 1182 0x80000002 0x00D5F6
192.168.90.0 200.0.0.4 1182 0x80000002 0x00623B
200.0.0.2 200.0.0.4 10 0x80000001 0x00C3D0
200.0.0.5 200.0.0.4 13 0x80000001 0x00A5EB
200.0.0.6 200.0.0.4 14 0x80000001 0x009BF4
200.0.0.9 200.0.0.4 14 0x80000001 0x008705
200.0.0.0/32 is subnetted
O IA 200.0.0.9 [110/783] via 192.168.10.6, 00:00:04, Serial0/0
O 200.0.0.2 [110/782] via 192.168.10.2, 00:00:04, Serial0/0
O 200.0.0.5 [110/782] via 192.168.10.5, 00:00:04, Serial0/0
O 200.0.0.6 [110/782] via 192.168.10.6, 00:00:06, Serial0/0
(2) After "area 0 range 200.0.0.0 255.255.255.0" command is configured:
Summary Net Link States (Area 4)
Link ID ADV Router Age Seq# Checksum
192.168.10.0 200.0.0.4 1223 0x80000002 0x00DD0E
192.168.25.0 200.0.0.4 1223 0x80000002 0x00D5F6
192.168.90.0 200.0.0.4 1223 0x80000002 0x00623B
200.0.0.0 200.0.0.4 14 0x80000001 0x003A6C
200.0.0.9 200.0.0.4 52 0x80000001 0x008705
The intra-area routes 200.0.0.2, 200.0.0.5, and 200.0.0.6 are removed. The
Type-3 LSA 200.0.0.0/24 is sourced into Area 4. The 200.0.0.9/32 is still
sent into Area 4.
(3) After applying Type-3 LSA filter to filter off all the remaining
200.0.0.x/32, as follows:
!
ip prefix-list TEST seq 5 deny 200.0.0.0/24 ge 32
ip prefix-list TEST seq 10 permit 0.0.0.0/0 le 32
!
router ospf 1
area 4 filter-list prefix TEST in
!
Summary Net Link States (Area 4)
Link ID ADV Router Age Seq# Checksum
192.168.10.0 200.0.0.4 1650 0x80000002 0x00DD0E
192.168.25.0 200.0.0.4 1650 0x80000002 0x00D5F6
192.168.90.0 200.0.0.4 1650 0x80000002 0x00623B
200.0.0.0 200.0.0.4 134 0x80000001 0x003A6C
This workaround appears to solve my problem :)
Thank you.
B.Rgds,
Lim TS
On 8/27/07, Serhat Aslan <serhatworks@gmail.com> wrote:
>
> Hi Toh,
>
> You can use area filter-list for LSA-3 or stub area solution that
> you mentioned.
>
> Serhat Aslan
>
>
> On 8/26/07, Toh Soon, Lim <tohsoon28@gmail.com> wrote:
> >
> > Hi Shine,
> >
> > Noted with thanks.
> >
> > Is there a workaround to this? I mean, the ability to summarize
> > inter-area routes on the ABR into another area using the "area range"
> > command?
> >
> > In my case if R4 learns 1000 inter-area routes and only 10 intra-area
> > routes, and all of them can be summarized by a single summary route, then
> > only the 10 intra-area routes are suppressed from entering Area 4 while the
> > 1000 inter-area routes will "leak" into Area 4. Maybe I can make Area 4 a
> > totally stubby area since it's connected to only one ABR (R4).
> >
> > Kindly comment.
> >
> >
> > Thank you.
> >
> > B.Rgds,
> > Lim TS
> >
> >
> > On 8/27/07, CCIE 19999 < ccie@iprimus.com.au> wrote:
> > >
> > > Lim,
> > >
> > > You are telling the router to summarise the routes originated from
> > > area 0 in
> > > the command. SO the router is doing exactly the same. It summarizes
> > > the
> > > routes originated in Area 0.
> > >
> > > HTH,
> > > Shine
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com ] On Behalf
> > > Of Toh
> > > Soon, Lim
> > > Sent: Monday, 27 August 2007 12:35 AM
> > > To: Serhat Aslan
> > > Cc: Cisco certification
> > > Subject: Re: OSPF "area range" command summarizes only intra-area
> > > routes?
> > >
> > > Hi Serhat,
> > >
> > > I'm sorry I don't fully understand your points.
> > >
> > > Without any area summarization, routers in Area 4 will learn all the
> > > 200.0.0.x/32 routes as inter-area routes.
> > >
> > > I want to summarize all these host routes so that routers in Area 4
> > > only see
> > > 200.0.0.0/24. I did it on the ABR (R4) using the "area 0 range
> > > 200.0.0.0
> > > 255.255.255.0" command.
> > >
> > > However, Area 4 still sees 200.0.0.9/32. Why? As far as R4 is
> > > concerned, the
> > > 200.0.0.9/32 is an inter-area route whereas the other 200.0.0.x/32 are
> > > intra-area routes.
> > >
> > > Appreciate your further advice.
> > >
> > >
> > > Thank you.
> > >
> > > B.Rgds,
> > > Lim TS
> > >
> > >
> > > On 8/26/07, Serhat Aslan < serhatworks@gmail.com> wrote:
> > > >
> > > > Hi Toh,
> > > > You made a wrong summarization. The steps of the summarizations
> > > are:
> > > > 0. The areas must be originated with the specified ABR. This means
> > > > intra-area routes.
> > > > 1. Choosing an Area, (the routes must be originated with the same
> > > area)
> > > > "area-range X"
> > > > 2. Area Routes Aggregation, (IP subnet mask supernetting)
> > > >
> > > > You forgot to consider step1.
> > > >
> > > > Serhat Aslan
> > > >
> > > >
> > > > On 8/26/07, Toh Soon, Lim < tohsoon28@gmail.com> wrote:
> > > >
> > > > > Hi Group,
> > > > >
> > > > > R4 is an ABR connected to Area 0 and Area 4. It learns the
> > > following
> > > > > routes
> > > > > in Area 0:
> > > > >
> > > > > Intra-area:
> > > > > 200.0.0.2/32
> > > > > 200.0.0.5/32
> > > > > 200.0.0.6/32
> > > > >
> > > > > Inter-area:
> > > > > 200.0.0.9/32
> > > > >
> > > > > I'm trying to summarize the above routes into Area 4, as follows:
> > > > >
> > > > > !
> > > > > router ospf 1
> > > > > area 0 range 200.0.0.0 255.255.255.0
> > > > > !
> > > > >
> > > > > Routers in Area 4 see the summary address 200.0.0.0/24. All
> > > component
> > > > > routes
> > > > > are suppressed except for 200.0.0.9/32 which "leaks" into Area 4.
> > > E.g.
> > > > >
> > > > > O IA 200.0.0.9/32 [110/784] via 192.168.40.1, 00:21:02,
> > > > > FastEthernet0/0
> > > > > O IA 200.0.0.0/24 [110/2] via 192.168.40.1, 00:17:49,
> > > > > FastEthernet0/0
> > > > >
> > > > >
> > > > > I suspect the "area range" command only summarizes intra-area
> > > routes.
> > > > > Can
> > > > > anyone clarify this? I might be missing something here.
> > > > >
> > > > >
> > > > > Thank you.
> > > > >
> > > > > B.Rgds,
> > > > > Lim TS
> > > > >
> > > > >
> > > _______________________________________________________________________
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