Re: OSPF: Stub Area vs Stub Network

Karim,

That link is to the Stub Router feature. Stub Network is a link that is not
used to reach any other networks, not necessarily one with a max metric.
Basically a link that has no other routers on the other end. For example, a
loopback will show up in the OSPF database as a stub network:

R1#sho ip osp database router 1.1.1.1

            OSPF Router with ID (1.1.1.1) (Process ID 1)

                Router Link States (Area 0)

  LS age: 18
  Options: (No TOS-capability, DC)
  LS Type: Router Links
  Link State ID: 1.1.1.1
  Advertising Router: 1.1.1.1
  LS Seq Number: 80000002
  Checksum: 0xD639
  Length: 48
  Area Border Router
  Number of Links: 2

    Link connected to: a Stub Network
     (Link ID) Network/subnet number: 1.1.1.1
     (Link Data) Network Mask: 255.255.255.255
      Number of TOS metrics: 0
       TOS 0 Metrics: 1

Stub Network is a type of the Router LSA (type 1). The types are

1 Point-to-point connection to another router
2 Connection to a transit network
3 Connection to a stub network
4 Virtual link

See RFC 2328 Appendix (Section A.4.2) for more details.

On Mon, Dec 14, 2009 at 7:55 AM, karim jamali <karim.jamali_at_gmail.com>wrote:

> Hi Syed,
>
> A stub network in OSPF occurs when the router advertises all its
> non-originated LSAs with a maximum metric, i.e. usually when the router
> needs to reload or go off the network so that the router will stop to be a
> transit path for non-locally originated networks..The command used is
> *max-metric
> router-lsa *under the OSPF process. There are various options that can be
> used with this command. The most common ones are using a timer (when this
> timer ends) the router will advertise those routes with a normal metric. A
> maximum metric for all non locally originated LSAs is advertised with
> maximum metric. You can configure it to keep advertising routes (LSAs) with
> maximum metric until BGP converges and then back to regular metrics.
>
> To read more about this feature:
>
> http://www.cisco.com/en/US/docs/ios/12_2t/12_2t4/feature/guide/ftospfau.html
>
> A stub area is a completely different concept. An area in OSPF can be
> defined to be stub i.e it will block LSA 4(Who redistributed the routes) &
> LSA 5(External Routes). All the routers in the area must agree on the stub
> flag to be neighbors. It is the ABR that does the filtering as routes are
> injected into the area.You can refer to this document for more information:
>
>
> http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094aaa.shtml#definestub
>
> Best Regards,
>
> Karim
>
>
> On Mon, Dec 14, 2009 at 12:40 PM, Syed Khalid Ali <
> khalid_khursheed_at_hotmail.com> wrote:
>
> > Dear Group:
> > Can any one explain the difference between two?
> > regards,Khalid
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Bryan Bartik
CCIE #23707 (R&S, SP), CCNP
Sr. Support Engineer - IPexpert, Inc.
URL: http://www.IPexpert.com
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