Re: OSPF- Area dummy area message

Hi Rajesh

OSPF area dummy area specifies that a LSA origination was prevented by a
conflicit with an existing LSA with the same LSID but a different mask.
OSPF resolve conflicts when multiple LSAs with the same prefix and
differing masks are advertised. When using this algorithm and host routes
are advertised there are situations where conflict resolution is impossible
and either the host route or the conflicting prefix is not advertised.

When an LSA is received for the same prefix twice with two different subnet
masks and the LSA ID is same , w will see this error, in ur case, it is a
PPP Link and ur a using a different subnet masks, both the configured
subnet mask and PPP Host route will be added and the there comes a LSA ID
for the same prefix with two different Subnet masks.

What you can do is that you can locate the prefix that is not advertised
and the conflicting prefix by entering the show ip route and show ip ospf
database commands and decide which route or prefix is more important to
advertise and take steps to prevent advertising the conflicting route or
prefix.

So the only fix proposed is to remove the unnecessary duplicate prefix, in
our case it should be the ppp peer route /32 .

Can you give no peer neighbor route under ppp and get rid of /32

And let me know the results.

Thanks
Hemanth Raj

On Tue, Nov 27, 2012 at 11:29 AM, Rajesh Prasad
<prasadrajesh1979_at_gmail.com>wrote:

> Did any one receive this message?
>
> On Mon, Nov 26, 2012 at 5:09 PM, Rajesh Prasad
> <prasadrajesh1979_at_gmail.com>wrote:
>
> > Hi,
> >
> > I am having a strange OSPF behavior, may be this is the way to prevent
> > loop in OSPF.
> >
> > This is the lab scenario.
> >
> > R5 is acting as a Hub and it is connected to R2 and R4 via
> > point-to-multipoint link and to R1 via point-to-point link. R1 and R2
> are
> > connected to R6 via EIGRP and redistributing EIGRP routes into R1 and R2.
> >
> > Now, as per my understanding on R1 and R2 the external LSA must be
> present
> > in database both on R1 (must be from R2 and its own) and on R2 ( From R1
> > and it own.)
> > But on both routers the database showing their own external LSA and does
> > not showing external LSA from others.
> >
> > After doing the debugging, i found that the routes are removed from the
> > database due to OSPF set the routes to Area dummy area and increased the
> > metric to 167772 learned from other borders routers
> >
> > Debuggin done on R1
> >
> > These routes are from R1
> >
> > OSPF process partial spfQ LSA id 54.1.3.0: mask 255.255.255.0, type 5
> > adv_rtr 150.1.1.1, age 3600, seq 0x80000002 (Area dummy area)
> > OSPF: Start partial processing Type 5 External LSA 54.1.3.0, mask
> > 255.255.255.0, adv 150.1.1.1, age 3600, seq 0x80000002, metric 167772
> >
> > Rack1R2#show ip ospf database external 204.12.1.0
> >
> > OSPF Router with ID (150.1.2.2) (Process ID 1)
> >
> > Type-5 AS External Link States
> >
> > LS age: 968
> > Options: (No TOS-capability, DC)
> > LS Type: AS External Link
> > Link State ID: 204.12.1.0 (External Network Number )
> > Advertising Router: 150.1.2.2
> > LS Seq Number: 80000009
> > Checksum: 0x1165
> > Length: 36
> > Network Mask: /24
> > Metric Type: 1 (Comparable directly to link state metric)
> > TOS: 0
> > Metric: 20
> > Forward Address: 0.0.0.0
> > External Route Tag: 300
> >
> >
> > Thanks in advance.
> >
> > Rgds,
> >
> > Rajesh
>
>
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-- 
Problems arise because we talk,problems are not solved because we don't
talk So good or bad talk to your affectionate one's freely.
Yours Friendly,
H P HEMANTH RAJ
CCIE#28593 (R&S)
Blogs and organic groups at http://www.ccie.net